Daf Yomi - Yevamos 7 - IS IT PREFERABLE TO VIOLATE A TOLDAH RATHER THAN AN AV (FOR ONE WHO IS DEATHLY ILL)?

The Tchebeiner Gaon (Dovev Meisharim, 3:82) inquires as to what the halacha would be in the following case. We are permitted to desecrate Shabbos for one who is deathly ill. Is it preferable to perform a labor which is only a toldah, a derivative of the av melocha, the primary categories of labor forbidden to do on Shabbos; or perhaps, there is no halachic difference since both are Biblically forbidden?

He ruled on this issue and cited support from our Gemora. It was taught in a braisa: A metzora whose eighth day (of purification) fell on Erev Pesach, but on that day had an emission of semen (resulting in the fact that he now cannot enter the Temple Mount to complete his purification process), and then immersed himself, the Chachamim said that although an ordinary tevul yom (one who has immersed in a mikvah but still has tumah on him until nightfall) may not enter the Temple Mount until nightfall, this one may enter in order to complete his purification process, thus enabling him to bring his pesach offering. It is preferable for a positive commandment that involves kares (pesach obligation) to override a positive commandment that does not involve kares (entering the Temple Mount while being a tevul yom).

Rabbi Yochanan maintains that it is only Rabbinically forbidden for a tevul yom to enter the Temple Mount.

Ula said: Why do we allow this tevul yom to enter? He answers: Since we would allow an ordinary metzora to enter the Temple Mount in order to complete his purification process, we allow a metzora who has had an emission of semen to enter as well.

Tosfos asks: Ula maintains that a partial entry into an area which is forbidden to enter is regarded as a full entry. If so, why do we limit this metzora, who is a tevul yom to insert his right ear, thumb and big toe into the Temple Courtyard, let him be permitted to enter entirely? What would be the distinction?

Tosfos answers: Entering completely into the Courtyard is regarded as being more severe than a partial entry. The Torah forbids a tevul yom from entering completely into the Courtyard explicitly, but a partial entry is only derived through the means of a hekesh (a Midrashic juxtaposition). Although both prohibitions are Biblical, the one that is written explicitly is stricter than the one which is merely derived from an exposition.

It emerges from here that a Biblical prohibition written explicitly is more stringent than one which is only derived through an exposition. He therefore posits that it would be preferable to engage in the labor which would only be violating a toldah rather than one which would constitute an av melocha. This is because a toldah is not written explicitly in the Torah.

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Daf Yomi - Yevamos 7 - Highlights

Rav Simi bar Ashi said: The Tanna who used the verse to teach us that Beis Din may not perform an execution on Shabbos did not need the verse because otherwise we would have thought that a positive commandment overrides a prohibition even though it involves kares. Rather, the verse was necessary, for otherwise we would have derived that Beis Din can execute a capital offender on Shabbos through the means of the following kal vachomer: Avodah (service in the Beis Hamikdosh) overrides Shabbos (the kohanim may perform the service on Shabbos), nevertheless, execution overrides avodah (a kohen, who has committed murder and was sentenced to death, Beis Din sends agents to bring him to be executed even if he wishes to perform the avodah); Shabbos, which is overridden by the avodah, shouldn’t an execution certainly override it (Beis Din should be permitted to perform an execution on Shabbos). This is why the verse “in any of your dwellings” was necessary; teaching us the halacha that Beis Din may not perform the execution. (6b – 7a)

The Gemora concludes that there is no source to teach us that the positive commandment of yibum will override the kares prohibition of taking his wife’s sister; nevertheless the verse aleha is required to teach us that he may not.

The Gemora explains: (One of the thirteen principles of Biblical exegesis is as follows: Something that was included in the general rule, and departed from that rule to teach something new, did not depart to teach only about itself, but rather to teach about the entire general rule.)

The Gemora cites an example where this principle is applied. It is written [Vayikra 17:20]: A person who eats flesh from the shelamim offering while his tumah is upon him, that soul shall be cut off from its people. Shelamim did not have to be mentioned separately, since they are included in the general rule of sacred offerings; why then are they mentioned separately? It is to teach us that only sacrifices brought to the altar are included in this rule, however animals dedicated to the Temple upkeep are excluded, and they are not subject to the kares penalty if eaten in a state of tumah.

The Gemora now explains how this principle is relevant to yibum. The prohibition of taking a brother’s wife was included in the general prohibition of all arayos (forbidden relations), and it was singled out in regards to yibum. This teaches us that just as this prohibition is permitted for the sake of yibum, so too all other arayos will be permitted for the sake of yibum.

The Gemora objects to this comparison between the two cases: By the halachos of tumah, both the general rule (all sacrifices) and the one singled out (shelamim) are dealing with prohibitions; whereas here by yibum, the general rule (all arayos) is dealing with the prohibition and the one which is singled out (brother’s wife) is permitted. (7a)

The Gemora states that this (the permissibility of yibum to a brother’s wife) is compared to a different principle. (One of the thirteen principles of Biblical exegesis is as follows: Something that was included in the general rule, and departed to be treated as a new case; you cannot return it to its general rule unless the Torah returns it explicitly.)

The Gemora cites an example where this principle is applied. It is written regarding a metzora [Vayikra 14:13]: He shall slaughter the (asham) lamb in the place where one slaughters the chatas and the olah, in a holy place. For the asham is like the chatas, for the kohen. What is this verse coming to teach us? Was it not already stated regarding the law of the asham that it was required to be slaughtered in the north? The Gemora answers: Since this asham departed from other asham’s insofar as it requires the placing of its blood on the right thumb and big toe of the metzora, one might think that it should not require blood applications or the burning of its sacrificial parts on the altar. The Torah, therefore, says: For the asham is like the chatas, teaching us that just like a chatas requires blood applications and the burning of its sacrificial parts on the altar, so too, the metzora’s asham requires blood applications and the burning of its sacrificial parts on the altar.

The Gemora concludes: Here also, by yibum, all arayos were prohibited and a brother’s wife was excluded from the general rule and became permitted for the sake of yibum; only a brother’s wife should be permitted, but all other prohibitions should remain prohibited even in a case of yibum. Accordingly, why did the Torah require a verse prohibiting yibum with one’s wife’s sister? (7a – 7b)

The Gemora offers another reason why the verse aleha is required to teach us that he may not perform a yibum on his wife’s sister. Perhaps we would have made a comparison to a brother’s wife. Just like one can perform a yibum on his brother’s wife (even though, she should be forbidden, if not for the mitzvah of yibum), so too, one can perform a yibum on his wife’s sister.

The Gemora asks: How can the two cases be compared? By a regular case of yibum, there is only one prohibition, whereas here, there are two prohibitions?

The Gemora answers: We might have thought that once the prohibition of taking a brother’s wife has been lifted, so too, the prohibition of taking his wife’s sister should also be lifted. (7b)

The Gemora asks: How do you know that this (when one prohibition is lifted, so too, another one should also be lifted) is a valid principle?

The Gemora answers: It was taught in a braisa: A metzora whose eighth day (of purification) fell on Erev Pesach, but on that day had an emission of semen (resulting in the fact that he now cannot enter the Temple Mount to complete his purification process), and then immersed himself, the Chachamim said that although an ordinary tevul yom (one who has immersed in a mikvah but still has tumah on him until nightfall) may not enter the Temple Mount until nightfall, this one may enter in order to complete his purification process, thus enabling him to bring his pesach offering. It is preferable for a positive commandment that involves kares (pesach obligation) to override a positive commandment that does not involve kares (entering the Temple Mount while being a tevul yom).

Rabbi Yochanan maintains that it is only Rabbinically forbidden for a tevul yom to enter the Temple Mount.

Ula said: Why do we allow this tevul yom to enter? He answers: Since we would allow an ordinary metzora to enter the Temple Mount in order to complete his purification process, we allow a metzora who has had an emission of semen to enter as well.

This is used as support for our logic regarding yibum. We might have thought that once the prohibition of taking a brother’s wife has been lifted, so too, the prohibition of taking his wife’s sister should also be lifted. This is why the verse aleha is needed to teach us that one cannot perform a yibum with his wife’s sister. (7b)

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Daf Yomi - Yevamos 6 - A TELEPHONE IS THE ANSWER

One might have thought that the mitzvah of honoring one’s father and mother overrides Shabbos (if a parent would instruct their son to violate the Shabbos, he would be obligated to listen); the Torah writes [Vayikra 19:3]: Every man: Your mother and father shall you revere, and My Shabbos’ shall you observe, I am HaShem your G-d. We infer from here: Everyone is obligated to honor HaShem, including the father and the mother. The Gemora assumes that the Torah is referring to a case where the parent said to his son, “Slaughter for me,” or Cook for me,” which is a kares prohibition. The reason he shouldn’t obey the father is because of the specific verse (mentioned above), but otherwise, the positive commandment of obeying one’s parent would override a prohibition, even one that consists of kares.

Tha Maharatz Chyus asks: Why should we think that the son is obligated to obey the father; the Gemora in Bava Metzia (62) teaches us that one is only obligated to honor his father if he is an “oseh ma’aseh amcha,” not if he is one that is not observing the mitzvos of HaShem?

The Ostroftzer Rebbe was once in Warsaw by one of his chasidim. The chasid proudly showed the Rebbe the new invention that was just installed in his house, a telephone.

The Rebbe took the telephone in his hands and 'sanctified' it with words of Torah.

He said: The Meiri in Yevamos asks: Why is a verse required to teach us that a son may not listen to his father when he instructs him to perform an aveira; the father is a rosha and the son is thus excluded from honoring him based on the Gemora in Bava Metzia that a father who is not "oseh ma'aseh amcha," one is not required to obey?

The Rebbe answered: It is referring to a case where the father calls the son on the telephone. The father is in one time zone, and it is already Motzei Shabbos, and the son is in a different time zone, where it is still Shabbos. One might think that the son is required to 'listen' to his father and answer the phone, the verse teaches us that everyone is obligated to honor HaShem and therefore the son should not obey the father.

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Daf Yomi - Yevamos 6 - Highlights

The Gemora had stated: We have successfully found a source teaching the principle that a positive commandment overrides a standard prohibition; where do we find that a positive commandment overrides a prohibition that is subject to the penalty of kares, thus requiring the verse aleha to teach that one cannot perform yibum on his wife’s sister?

The Gemora continues: Perhaps it can be derived from the mitzvah of honoring one’s father and mother. It was taught in a braisa: One might have thought that the mitzvah of honoring one’s father and mother overrides Shabbos (if a parent would instruct their son to violate the Shabbos, he would be obligated to listen); the Torah writes [Vayikra 19:3]: Every man: Your mother and father shall you revere, and My Shabbos’ shall you observe, I am HaShem your G-d. We infer from here: Everyone is obligated to honor HaShem, including the father and the mother. The Gemora assumes that the Torah is referring to a case where the parent said to his son, “Slaughter for me,” or Cook for me,” which is a kares prohibition. The reason he shouldn’t obey the father is because of the specific verse (mentioned above), but otherwise, the positive commandment of obeying one’s parent would override a prohibition, even one that consists of kares.

The Gemora objects to this proof: The Torah is referring to a case where the parent instructed him to lead a loaded animal on Shabbos, which is not a kares prohibition. (This is referred to as the prohibition of mechamer, leading an animal with a load on it on Shabbos. This prohibition does not involve a death punishment, even though all other Shabbos prohibitions do involve the death penalty.)

The Gemora objects to this interpretation: If the verse is referring to a standard prohibition and nevertheless, the positive commandment of honoring one’s parents does not override the prohibition of mechamer, let us derive from here that positive commandments cannot override a prohibition?

Perhaps you would answer that the prohibitions pertaining to Shabbos are stricter than a standard prohibition and therefore we would not be able to compare this situation with other prohibitions (a positive commandment cannot override a Shabbos prohibition, but it can override a regular prohibition).

The Gemora proves from a braisa that the prohibitions pertaining to Shabbos are similar to other prohibitions.

It was taught in a braisa: If a kohen’s father tells his son to become tamei or not to return a lost object, he should not obey him because it is written [Vayikra 19:3]: Every man: Your mother and father shall you revere, and My Shabbos’ shall you observe, I am HaShem your G-d. We infer from here: Everyone is obligated to honor HaShem, including the father and the mother. Although the verse is referring to the prohibition of Shabbos, nevertheless, we derive from there regarding all prohibitions. It is evident that the Tanna does not consider a Shabbos prohibition stricter than a regular prohibition. (5b – 6a)

The Gemora concedes that it is evident that the Torah is referring to a case where the parent instructed the son to slaughter or cook for him, which involves a kares prohibition. The fact that we needed a verse to teach us that he should not obey his parent’s command indicates that a positive commandment can override a prohibition that involves kares. Yet, this still will not explain why the verse aleha is required to teach us that a man cannot perform yibum on his wife’s sister. In the case where the parent instructed the son to slaughter or cook for him, the prohibited act of slaughtering or cooking is essential for the fulfillment of the commandment (and that is why one might think that it would be permitted to do); however in the case of yibum, it is not essential to violate the prohibition of living with one’s wife’s sister in order to fulfill the mitzvah since the mitzvah can be observed by performing chalitzah. Accordingly, it should never enter our mind that the mitzvah shall override the kares prohibition of his wife’s sister since the mitzvah can be fulfilled through performing a chalitzah; why is the verse aleha required? (6a)

The Gemora presents another source: Perhaps it can be derived from the mitzvah of building the Beis Hamikdosh. It was taught in a braisa: One might have thought that the mitzvah of building the Beis Hamikdosh should override Shabbos; the Torah writes [Vayikra 19:3]: My Shabbos’ shall you observe, and My Sanctuary shall you revere; I am HaShem. We infer from here: Everyone is obligated to honor HaShem, including the Sanctuary. The Gemora assumes that the Torah is referring to a case of building and destroying, which is a kares prohibition. The reason one should not violate the Shabbos is because of the specific verse (mentioned above), but otherwise, the positive commandment of building the Beis Hamikdosh would override a prohibition, even one that consists of kares.

The Gemora objects to this proof: The Torah is referring to the prohibition of leading a loaded animal on Shabbos, which is not a kares prohibition.

The Gemora objects to this interpretation: If the verse is referring to a standard prohibition and nevertheless, the positive commandment of building the Beis Hamikdosh does not override the prohibition of mechamer, let us derive from here that positive commandments cannot override a prohibition?

Perhaps you would answer that the prohibitions pertaining to Shabbos are stricter than a standard prohibition and therefore we would not be able to compare this situation with other prohibitions (a positive commandment cannot override a Shabbos prohibition, but it can override a regular prohibition).

The Gemora proves from a braisa that the prohibitions pertaining to Shabbos are similar to other prohibitions.

It was taught in a braisa: If a kohen’s father tells his son to become tamei or not to return a lost object, he should not obey him because it is written [Vayikra 19:3]: Every man: Your mother and father shall you revere, and My Shabbos’ shall you observe, I am HaShem your G-d. We infer from here: Everyone is obligated to honor HaShem, including the father and the mother. Although the verse is referring to the prohibition of Shabbos, nevertheless, we derive from there regarding all prohibitions. It is evident that the Tanna does not consider a Shabbos prohibition stricter than a regular prohibition.

The Gemora concedes that it is evident that the Torah is referring to a case of building and destroying on Shabbos, which is a kares prohibition. The fact that we needed a verse to teach us that one should not build or destroy on Shabbos indicates that a positive commandment can override a prohibition that involves kares. Yet, this still will not explain why the verse aleha is required to teach us that a man cannot perform yibum on his wife’s sister. In the case of building and destroying for the Beis Hamikdosh, the prohibited act of building and destroying is essential for the fulfillment of the commandment (and that is why one might think that it would be permitted to do); however in the case of yibum, it is not essential to violate the prohibition of living with one’s wife’s sister in order to fulfill the mitzvah since the mitzvah can be observed by performing chalitzah. Accordingly, it should never enter our mind that the mitzvah shall override the kares prohibition of his wife’s sister since the mitzvah can be fulfilled through performing a chalitzah; why is the verse aleha required?

The Gemora asks: We do not need a verse to teach us that the positive commandment does not override a prohibition of kares even when the prohibition is essential for the fulfillment of the commandment since we have previously derived this from the verse concerning the mitzvah of honoring one’s parents. (6a)

The Gemora states: The verse juxtaposing the observance of Shabbos with the revering of the Beis Hamikdosh is actually teaching us something entirely different (and we cannot derive from there that a positive commandment will override a kares prohibition). It was taught in a braisa: Just like one does not revere the Shabbos, but reveres the One who instructed us to observe the Shabbos, so too one is not required to revere the Beis Hamikdosh. Rather, one is required to revere the One who instructed us regarding the building of the Beis Hamikdosh.

How does one display reverence of the Beis Hamikdosh? One should not enter the Temple Mount with his stick, shoe, and money belt or with the dust upon his feet. One should not use it as a shortcut and spitting is forbidden based on a kal vachomer.

This halacha is applicable even when the Beis Hamikdosh is not in existence. This is derived from the fact that the Torah juxtaposed the observance of Shabbos to the reverence of the Beis Hamikdosh. Just as the obligation to observe Shabbos is forever, so too, the reverence of the Beis Hamikdosh is forever. (6a – 6b)

The Gemora posits another source (as to why we would think that the mitzvah of yibum overrides the prohibition of living with his wife’s sister even though it involves kares): It can be derived from the prohibition regarding kindling on Shabbos.

The school of Rabbi Yishmael taught in a braisa: It is written [Shmos 35:3]: You shall not kindle a fire in any of your dwellings on the Shabbos day. What do we learn from here?

The Gemora asks: How can you ask what is learned from this verse? There is a braisa that presents a dispute between Rabbi Yosi and Rabbi Nosson regarding this verse. It was taught in a braisa: Rabbi Yosi said that this verse teaches us that kindling on Shabbos is merely a prohibition (and incurs lashes for violating it and not kares or stoning). Rabbi Nosson said: It is to teach us that one is liable for punishment for violating one melocha (labor) on Shabbos. (Otherwise, we would have thought that one incurs a punishment only if he violates all thirty-nine melochos.)

Rava answers: The Tanna was questioning the word “dwellings.” Why was it necessary for the Torah to write that one cannot kindle in any of your dwellings, indicating that it is forbidden outside of Eretz Yisroel, as well; Shabbos is a personal obligation, and personal obligations apply even outside Eretz Yisroel (unlike a mitzvah which is dependent on land, where the obligation will only be in Eretz Yisroel)?

A student answered in the name of Rabbi Yishmael: The word “dwellings” in this verse is used for a gezeirah shavah (one of the thirteen principles of Biblical hermeneutics - it links two similar words from dissimilar verses in the Torah) to teach us that this verse is referring to a Beis Din, and even a Beis Din cannot perform an execution (for example, burning) on one who committed a capital offense on Shabbos.

The Gemora assumes that this braisa is following Rabbi Nosson’s opinion, who maintains that one who kindles on Shabbos incurs the penalty of kares, and yet, we required a verse to teach us that Beis Din cannot perform an execution on one who committed a capital offense on Shabbos. Otherwise, we would have thought that the positive commandment of executing a capital offender would override the prohibition of kindling on Shabbos. We can derive from here that in other instances, a positive commandment will override a prohibition that involves kares. This is why we would have thought that one can perform yibum on his wife’s sister, if not for the verse of aleha.

The Gemora objects to this proof and states that perhaps the braisa is following Rabbi Yosi’s opinion, who holds that kindling is merely a prohibition that incurs lashes if violated, but not the penalty of kares.

The Gemora concludes: Even if the Tanna is following Rabbi Yosi’s opinion, there would still be a proof that a positive commandment overrides a kares prohibition. Rabbi Yosi only said that kindling was merely a prohibition (and not subject to kares) in regards to a regular case of kindling. Beis Din’s kindling (when it is preparing an execution by burning) involves the cooking of a lead wick (a wick of lead is heated and then the molten lead is poured down the offender’s throat). Rav Ashi had said that there is no difference between cooking this (lead) wick and cooking herbs. Cooking is obviously a melocha which is subject to kares. It emerges that even if the Tanna follows Rabbi Yosi’s viewpoint, we can see that a positive commandment overrides a kares prohibition and that is why we needed aleha to teach us that a man may not perform a yibum on his wife’s sister. (6b)

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Daf Yomi - Yevamos 5 - A POSITIVE COMMANDMENT OVERRIDING TWO PROHIBITIONS

Reb Moshe Rozmerin in Dvar Moshe states that the Rambam maintains that one who rounds the corners of his head has violated two prohibitions; one for cutting his payos (corners), and another for following in the statutes of the non-Jews.

Our Gemora states that the positive commandment for the metzora to remove all his hair overrides the prohibition of rounding the corners on one’s head.

According to the Rambam, it is actually overriding two prohibitions.

Tosfos above (3b) discussed this issue and did not cite our Gemora as a proof. Other Rishonim maintain that a positive commandment cannot override two prohibitions.

A question is brought in the name of the Lubliner Gaon: The Gemora later (20b) states regarding a widow falling to yibum to a Kohen Gadol that it is a situation where the positive commandment of yibum can possibly override the prohibition of a Kohen Gadol marrying a widow. He asks: There are two prohibitions for a Kohen Gadol to marry a widow; one is lo yikach (he shall not take her), and the other is lo yechallel (he shall not desecrate the kehuna). How can the positive commandment of yibum override two prohibitions?

Reb Chaim Ozer in Achiezer (Even Ezer, 4) answers: The Rishonim concede when the two prohibitions are dependent on each other, that the positive commandment can override both prohibitions. The basis for the prohibition of desecrating the kehuna is because it is an illicit relationship; once the mitzvah of yibum overrides the prohibition of lo yikach, it becomes a permitted relationship and there will be no prohibition of lo yechallel.

[It would seem to me that this is dependent on how we understand that a positive commandment cannot override two prohibitions. We can explain that each prohibition strengthens one another and the positive commandment cannot override any of them; or perhaps the positive commandment does override one of the prohibitions, but it does not have the capabilities to override the second one. Reb Chaim Ozer would be in accordance with the latter explanation.]

According to the Achiezer, we can answer the Dvar Moshe’s question. The positive commandment for the metzora to cut his hair overrides the prohibition against rounding the corners of one’s head, and consequently, there will be no prohibition of following in the statutes of the non-Jews.

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Daf Yomi - Yevamos 5 - Highlights

The Gemora seeks to find a source according to the Chachamim (who maintain that the words wool and linen are not extra and therefore the juxtaposition cannot be expounded) that a positive commandment overrides a prohibition.

The Gemora answers: It is derived from the word rosho, his head, which is written in the verses discussing a metzora shaving his head (part of his purification process). This is a superfluous word because the Torah had stated already that he shall shave off all his hair; why is it said? It is written elsewhere [Vayikra 19:27]: You shall not round the corners of your head (cutting the ‘payos,’ corners of the hair from his temples). I would have thought that this prohibition includes the metzora, and he cannot shave his sideburns, the possuk says rosho, teaching us that he shaves his entire head.

The Gemora explains that this Tanna maintains that one who shaves off all his hair from his head (like the metzora is required to do) has in fact violated the prohibition of rounding the corners on his head.

It emerges that we learn that the positive commandment for the metzora to remove all his hair overrides the prohibition of rounding the corners on one’s head. We derive from here that all positive commandments can override a prohibition.

The Gemora objects: Perhaps the reason the positive commandment can override this prohibition is because the prohibition against rounding the corners of one’s head is a prohibition that is not applicable to all (a woman is not subject to this prohibition). (We cannot derive from here to other instances, where the prohibition is a universal one.) (5a)

The Gemora presents another source: It was taught in a braisa: What is derived from the word rosho, his head? It is written regarding a nazir [Bamidbar 6:5]: A razor shall not pass over his head. (This prohibition forbids him to shave any part of his head with a razor.) I would have thought that one who is a metzora and a nazir would not be permitted to shave his head (even for the purification process), the Torah teaches us that the positive commandment for a metzora to shave his head overrides the prohibition of the nazir against shaving his head with a razor. We can derive from here to all instances that a positive commandment overrides a prohibition.

The Gemora objects: Perhaps the reason the positive commandment can override this prohibition is because the prohibition forbidding a nazir to shave is a lenient one, for a nazir can release himself from his prohibitions by imploring a sage to annul his vow. (We cannot derive from here to other instances, where the prohibition is a strict one.)

The Gemora returns to the juxtaposition of tzitzis and shatnez. The Gemora explains that there is an extra word in the verse even according to the Chachamim. The Torah could have written: You shall make yourself tzitzis (fringes); why did the Torah write gedilim, twined fringes? It is to make the verse available for expounding; the fact that the Torah juxtaposes these two verses, teach us that one can make tzitzis even in a case of shatnez. This indicates that a positive commandment can override a prohibition.

The Gemora rejects this explanation, as well: The word gedilim is not extra since it teaches us that each corner of the garment must have four threads.

The Gemora states: There is still an extra word in this verse. The Torah could have written: You shall not wear shatnez, wool and linen. Why did the torah write the word together? It is to make the verse available for expounding; the fact that the Torah juxtaposes these two verses, teach us that one can make tzitzis even in a case of shatnez. This indicates that a positive commandment can override a prohibition.

The Gemora rejects this explanation, as well: the word together is not extra since it is teaches us that if one fastens a woolen garment to a linen garment with two passes of the needle (forming a complete stitch), he may not wear the garment, but if they are fastened with only one pass of the needle, it is not regarded as a connection, and they may be worn.

The Gemora states: There is still an extra word in this verse. The Torah could have written: You shall not wear wool and linen together. Why did the torah write the word shatnez? It is to make the verse available for expounding; the fact that the Torah juxtaposes these two verses, teach us that one can make tzitzis even in a case of shatnez. This indicates that a positive commandment can override a prohibition.

The Gemora rejects this explanation, as well: The word shatnez is not extra since it teaches us that one has not violated the prohibition against wearing shatnez unless the wool and linen threads are combed, spun and woven together.

The Gemora answers: The word shatnez teaches us everything. The word is extra and therefore it is available for expounding; the fact that the Torah juxtaposes these two verses, teach us that one can make tzitzis even in a case of shatnez. This indicates that a positive commandment can override a prohibition. However, if this word were intended only for this teaching, the Torah could have written a more common term, such as kilayim, meaning mixture; why did the Torah use the term shatnez? It is to learn the additional halacha that one has not violated the prohibition against wearing shatnez unless the wool and linen threads are combed, spun and woven together. (5a – 5b)

The Gemora states: We have successfully found a source teaching the principle that a positive commandment overrides a standard prohibition; where do we find that a positive commandment overrides a prohibition that is subject to the penalty of kares, thus requiring the verse aleha to teach that one cannot perform yibum on his wife’s sister?

The Gemora states: Perhaps it can be derived from the positive mitzvah of bris milah (circumcision), which can be performed even on Shabbos, which is subject to the penalty of kares.

The Gemora objects: Bris milah is different because there were thirteen covenants sealed in regards to this commandment.

Perhaps it can be derived from the positive mitzvah of korban pesach, which can be performed even on Shabbos, which is subject to the penalty of kares.

The Gemora objects: Korban pesach is different because there is a penalty of kares for one who refrains from offering the korban pesach.

Perhaps it can be derived from the positive mitzvah of offering the daily korban tamid, which can be performed even on Shabbos, which is subject to the penalty of kares.

The Gemora objects: Korban tamid is different because it is a korban, which is offered constantly.

The Gemora proposes to derive this principle from all three of these mitzvos together. This is rejected because all three mitzvos existed before the Giving of the Torah. (5b)

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Daf Yomi - Yevamos 4 - WHICH IS GREATER? A POSITIVE COMMANDMENT OR A NEGATIVE ONE

The Gemora states that a positive commandment can override a prohibition that carries with it a standard punishment.

The question is asked: Why is it that a positive commandment overrides a prohibition and yet the punishment for transgressing a prohibition is much more severe than the punishment for not fulfilling a positive commandment?

Reb Yossie Schonkopf said over a parable from his Rebbe: A trucker is hired to transport a load across the country and the owner warns him not to go beyond the speed limit, not to crash the vehicle and to follow all the road instructions. If the trucker does everything perfectly but doesn't unload the goods at his destination; rather, he arrives at the destined location and immediately turns around carrying the same load, what is accomplished by the fact that the trucker obeyed the speed limit and followed all the rules?

The meaning is as follows: Our mission in life is to accomplish in this world and 'build the love towards HaShem,’ therefore, this building overrides the transgressions. The prohibitions are only there to protect what has been built and not to suffocate the building.

This concept is elucidated by the Ramban in Parshas Yisro. He states that the fulfillment of a positive commandment is based on ahavas HaShem, loving HaShem and refraining from committing a transgression is based on yiras HaShem fearing HaShem. It is a higher level to serve HaShem through love, but it is worse to violate a prohibition, which is based upon fearing HaShem.

My brother, Reb Ben asked a similar question: The Gemora states that a positive commandment will override a negative commandment when both commandments are performed simultaneously. It is noteworthy that the Gemora in Sota states that a mitzvah cannot extinguish an aveira, a sin, yet an aveira can extinguish a mitzvah. Apparently, the principle that a positive commandment can override a negative commandment is not a contradiction to this Gemora. Perhaps the idea is that when one performs an aveira intentionally, he has rebelled against HaShem, and it is not possible for one to appease HaShem with a mitzvah when he has just committed an act of rebellion. When one is simultaneously overriding the negative commandment by performing a positive commandment, however, he is demonstrating that he is fully aware that he is performing a negative commandment, yet he is permitted by the Torah to override the negative commandment. This principle allows him to perform the positive commandment and be rewarded for its performance.

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Daf Yomi - Yevamos 4 - SHATNEZ BY TZITZIS

It is written [Devarim 22: 11 - 12]: You shall not wear shatnez (wool and linen together). You shall make for yourself tzitzis (twined fringes). The fact that the Torah juxtaposes these two verses, teach us that one can make tzitzis even in a case of shatnez. This indicates that a positive commandment can override a prohibition.

The commentators ask from the Gemora below (4b): The Gemora states: If the Torah would have only written the passuk in Vayikra: and a garment that is a mixture of shatnez shall not come upon you, we would have thought that placing shatnez upon oneself in any manner would be forbidden, and even garment sellers would be prohibited from wearing shatnez (they merely drape themselves with the garments in order to exhibit them without a specific intent for the warmth which these garments offer). This is why the Torah wrote in Devarim: You shall not wear shatnez, teaching us that it is forbidden to wear shatnez only by a wearing that offers physical pleasure (and since a garment seller does not wear the garment for that intent, it will be permitted for him).

Accordingly, what is the proof from the fact that one can wear a garment of tzitzis which contains shatnez that a positive commandment can override a prohibition; perhaps one can don a garment of tzitzis that contains shatnez because the prohibition is only when wearing a garment that provides physical pleasure and his intention is for that purpose? One who is wearing tzitzis should not be regarded as deriving pleasure because of the dictum of “mitzvot lav le’henos nitnu” – mitzvos were not given for the purpose of pleasure.

According to the Ran, this is not a question, for he says that the principle of “mitzvot lav le’henos nitnu” is not applicable when there is a physical pleasure; here, the garment is providing physical warmth and therefore, it should be prohibited if not for the fact that the positive commandment can override the prohibition.

However, the Rashba disagrees and maintains that we don’t consider any benefit that one receives during the fulfillment of a mitzvah; if so, let us say that one is permitted to wear tzitzis containing shatnez because he is not deriving any pleasure?

Reb Shmuel Rozovsky answers: The prohibition of shatnez is merely not to wear a garment containing shatnez; there is a condition that it is only regarded as wearing if he is deriving pleasure.

One who is wearing a garment of tzitzis is wearing the garment and deriving pleasure. While it’s true that the performance of the mitzvah negates the benefit he is receiving, he is still wearing the garment and it should be prohibited, if not for the fact that the positive commandment overrides this prohibition.

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Daf Yomi - Yevamos 4 - Highlights

The Gemora required a source to teach us that one cannot perform yibum on his wife’s sister.

The Gemora infers from here that otherwise, one would have been permitted to perform yibum on his wife’s sister.

The Gemora asks: Why would this have been allowed?

The Gemora answers: This would have been based on the principle that a positive commandment can override a prohibition. The positive commandment of yibum would have overridden the prohibition against living with ones wife’s sister.

The Gemora objects to this explanation: A positive commandment can override a prohibition that carries with it a standard punishment, whereas a positive commandment cannot override a prohibition that is punishable by kares.

Furthermore, the Gemora inquires as to where the source is that a positive commandment can override even an ordinary prohibition.

It is written [Devarim 22: 11 - 12]: You shall not wear shatnez (wool and linen together). You shall make for yourself tzitzis (twined fringes). The fact that the Torah juxtaposes these two verses, teach us that one can make tzitzis even in a case of shatnez. This indicates that a positive commandment can override a prohibition.

Rabbi Elozar cites a Scriptural source demonstrating that we can expound Scriptural verses through juxtaposition. (3b – 4a)

Rav Yosef says: Even if generally, one does not expound Scriptural verses in the Torah through juxtapositions, in Sefer Devarim, he would. He proves this from Rabbi Yehudah, who maintains that we do not expound juxtapositions, but in Devarim, he does.

The Gemora proceeds to prove that Rabbi Yehudah does not expound juxtapositions anywhere in the Torah except in the Book of Devarim. (4a)

The Gemora asks: Why are the verses in Devarim different than the rest of the Torah?

The Gemora answers: Either it is because it is obvious that the two verses were juxtaposed for the sake of expounding them or alternatively, it is because one of the verses is extra and thus available for exposition. (4a – 4b)

The Gemora proceeds to explain why we would be justified to expound the juxtaposition regarding tzitzis and shatnez even according to Rabbi Yehudah.

It is obvious that these two verses were juxtaposed for the sake of expounding them, for otherwise, the passage regarding tzitzis should have been written in Parashas Shelach, which is the primary source for the obligation to wear a four-cornered garment of tzitzis.

Alternatively, it is because the verse here is certainly extra and thus available for exposition. It is written [Vayikra 19:19]: and a garment that is a mixture of shatnez shall not come upon you. It is not necessary to write the verse in Devarim: You shall not wear shatnez. It is apparently extra to teach us that the positive commandment of tzitzis overrides the prohibition against wearing shatnez.

The Gemora asks: These two verses are both necessary. If the Torah would have only written the passuk in Vayikra: and a garment that is a mixture of shatnez shall not come upon you, we would have thought that placing shatnez upon oneself in any manner would be forbidden, and even garment sellers would be prohibited from wearing shatnez (they merely drape themselves with the garments in order to exhibit them without a specific intent for the warmth which these garments offer). This is why the Torah wrote in Devarim: You shall not wear shatnez, teaching us that it is forbidden to wear shatnez only by a wearing that offers physical pleasure (and since a garment seller does not wear the garment for that intent, it will be permitted for him).

If the Torah would have only written the passuk in Devarim: You shall not wear shatnez, we might have thought that there is a prohibition to wear shatnez, which provides a good deal of physical pleasure, but one would be permitted to place a garment on himself without wearing it. This is why the Torah wrote in Vayikra: and a garment that is a mixture of shatnez shall not come upon you, teaching us that even that is forbidden.

It emerges that both verses are necessary and not extra to expound the juxtaposition to tzitzis.

The Gemora answers: While it’s true that both verses are necessary, there are still superfluous words in the verse. The verse stated: You shall not wear shatnez wool and linen together. It is unnecessary to say that shatnez consists of wool and linen. The verse in Vayikra stated: and a garment that is a mixture of shatnez shall not come upon you, and it was taught in the school of Rabbi Yishmael that whenever the Torah refers to a garment and the Torah does not specify what type of garment we are discussing, it is referring to a garment of wool and linen. Why does the Torah find it necessary to write that shatnez is wool and linen? It is extra to indicate that we can expound the juxtaposition of tzitzis to shatnez to teach us that the positive commandment of tzitzis overrides the prohibition against wearing shatnez. (4b)

The Gemora asks: Why is it necessary to expound the juxtaposition that tzitzis overrides the prohibition against wearing shatnez according to the school of Rabbi Yishmael; they have a much better source than that? It is written regarding the obligation of tzitzis [Bamidbar 15:38]: and they shall make themselves tzitzis on the corners of their garments. The school of Rabbi Yishmael maintains that whenever the Torah says garment, it is referring to wool and linen, and we know that the Torah requires one thread of techeiles wool (blue dye from the blood of the chilazon). It emerges that the Torah is obligating us to place a woolen thread on a linen garment, which would constitute shatnez.

The Gemora answers: We might have thought that one should use a thread of techeiles wool only on a garment of wool, and one should use linen strings when he is wearing a linen garment; the juxtaposition teaches us that one can place woolen strings on a linen garment and linen strings on a woolen garment. (4b)

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Daf Yomi - Yevamos 3 - REB AKIVA EIGER’S VELTZ KASHA

Rabbi Akiva Eiger asks the following question: Why do we need a passuk of "litzror" mentioned in the braisa, to derive the prohibition against marrying a tzaraas tzarah (co-wife’s co-wife)? Once the Torah prohibits performing yibum with a tzarah (co-wife), she remains forbidden to her (deceased) husband's brothers because of the prohibition of eishes ach (the wife of one's brother). Accordingly, her status is the same as that of any other ervah, and her tzarah should be no different from any tzarah of an ervah.

Although the prohibition against marrying ones brother’s wife is normally suspended in situations of yibum, the Mishna teaches in another case (eishes achiv she'lo hayah b'olamo - the wife of his brother who was not in his world (this brother and the yavam were not alive at the same time)) that the prohibition of eishes ach has the capability to prohibit the woman to the brother with whom she otherwise would have performed yibum with, and the Gemora does not find it necessary to seek an extra source for this.

In that case, a brother born after the death of his older (and childless) brother may not perform yibum, because he was "not in the world at the same time" as his brother and thus his brother's wife remains forbidden to him as an eishes ach. Similarly, her tzarah is also forbidden to him because she is the tzarah of an ervah. Just as in this case, an extra source is not required to teach us the prohibition of the tzarah of an ervah, a source should not be required to teach us the prohibition of the tzarah of a tzarah. (Kollel Iyun HaDaf assisted us immensely in the writing of this question.)

Reb Elchonon Wasserman (Kovetz Heoros 2:4) answers: The only time that the ervah of eishas ach can exempt the tzorah from yibum is when the ervah became exempt herself on the account of eishes ach; however, when the yevamah became exempt from yibum on the account of a different reason, resulting in there being a prohibition of eishas ach; she will not exempt the tzorah from yibum.

In the case where the two brothers were not alive at the same time, the yevamah is exempt from yibum on the account of being an eishes ach; she will exempt the tzorah, as well. A tzoras ervah is not exempt because she is an eishes ach; she is only exempt because she is a co-wife of an ervah; consequently, she becomes prohibited on the account of eishes ach, but she cannot exempt her tzorah. The Gemora requires a source to teach us that the tzorah has the ability to exempt her tzorah, as well.

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Daf Yomi - Yevamos 3 - Highlights

The Gemora states that the exemptions regarding the fifteen women listed in the Mishna are all derived from the verse in the Torah discussing his wife’s sister.

The Gemora asks: Why didn’t the Mishna list the case of his wife’s sister first?

The Gemora answers: The Mishna listed the fifteen women according to the closeness of their relationship with the yavam. The closest ones are his daughter, and his daughter’s daughter and his son’s daughter since these three are his blood relatives. Since the Tanna listed three generations descending from the man, he listed three generations descending from the yavam’s wife, i.e. his wife’s daughter, and her daughter’s daughter and her son’s daughter. Once the Mishna listed three generations descending from her (yavam’s wife), he decided to list three generations ascending from her, i.e. his mother-in-law, and his mother-in-law’s mother and his father-in-law’s mother. He then listed the yavam’s maternal sister and his mother’s sister since they are his blood relatives (more than his daughter-in-law, who is only related through her marriage to his son). Once he was discussing prohibitions pertaining to sisters, he mentioned his wife’s sister. Of the three remaining women (his daughter-in-law, his maternal brother’s wife and the wife of his brother who was not in his world, who are all not blood relatives), the Tanna should have listed his daughter-in-law first (because her prohibition is the most severe; stoning compared to kares); however, since we were discussing prohibitions dealing with siblings, the Tanna listed his maternal brother’s wife and the wife of his brother who was not in his world and concluded with his daughter-in-law. (2b – 3a)

The Gemora asks: Why does the Mishna say that these fifteen women exempt their co-wives; let the Mishna say that they forbid their co-wives?

The Gemora answers: If the Mishna would say forbid, one might think that it is forbidden to perform a yibum with her, but one is required to perform chalitzah; the Tanna teaches us that she is exempt from chalitzah, as well.

The Gemora asks: Let the Mishna say that these fifteen women forbid their co-wives from chalitzah?

The Gemora answers: What would be wrong with performing a chalitzah with an ervah?

The Gemora rejects this answer: If we would allow the yavam to perform a chalitzah, an ignorant person might mistakenly think that yibum is also permitted and he will perform yibum with an ervah.

The Gemora concludes: Since a co-wife of the ervah becomes forbidden only in situations which involve the mitzvah of yibum (the deceased was a brother of this person), and not in any other situation (any time that a man is married to someone else’s ervah); the Mishna uses the term “exempt,” indicating that this ruling applies only in situations of yibum. (3a)

The Mishna had stated: Fifteen women exempt their co-wives and the co-wives of their co-wives from chalitzah and from yibum.

The Gemora asks: Would it have not been sufficient for the Mishna to say that they are exempt from yibum?

The Gemora answers: If the Mishna would have only said that they are exempt from yibum, we might have thought that there would be a requirement for chalitzah; the Mishna teaches us that whoever is subject to yibum is subject to chalitzah and whoever is not subject to yibum is not subject to chalitzah.

The Gemora asks: Let the Mishna say that they are exempt from yibum and chalitzah (reversing the order) or it can say that they are exempt from chalitzah (and we would understand that he cannot perform a yibum)?

The Gemora answers: The Mishna is following the viewpoint of Abba Shaul, who maintains that the mitzvah of chalitzah takes precedence over the mitzvah of yibum (since he might not have pure intentions); it is for this reason that the Tanna mentions chalitzah before yibum. (3a)

The Gemora asks: From where do we derive all the halachos listed in the Mishna?

The Gemora cites a braisa which provides a Scriptural verse (in the passages discussing the prohibition of living with ones wife sister when his original wife is still alive) teaching us that one cannot perform a yibum on his wife’s sister. It is also derived from those verses that he cannot take the co-wife of his wife’s sister and the co-wife of his wife’s sister’s co-wife. The braisa continues to teach us that we derive from here that he cannot perform yibum on any ervah, her co-wife or her co-wife’s co-wife. (3b)

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Daf Yomi - Yevamos 2 - WHY IS YEVAMOS FIRST?

The Tosafos Yeshanim asks why Seder Nashim begins with Masechta Yevamos, which discusses the marriage laws of a widow whose husband died childless. It would be more appropriate to begin the Seder with Kidushin, which would be a more positive introduction to the laws of marriage.

Tosafos Yeshanim answers that the previous Seder (Moed) ended with Moed Katan, which deals largely with aveilus, and thus leads naturally to Yevamos (which deals with the brother who dies childless).

Alternatively, he answers that this Mishna teaches us all the women that one would be prohibited from marrying; afterwards, we can learn regarding the mitzvah of kidushin, marriage.

Also, the mitzvah of yibum was the first mitzvah pertaining to women mentioned in the Torah, as it is written regarding Tamar.

The Acharonim point out that the first answer of the Tosafos Yeshanim is the opinion of the Rambam (Yibum1:1) and the Chinuch (598), who consider Yibum to be a mitzvah only for the man (i.e. the brother). Consequently, the Rambam and the Chinuch would not agree with the last answer of the Tosfos Yeshanim.

However, the Pnei Yehoshua (Kesubos 40a) holds that other Rishonim consider the widow to be equally obligated in yibum. As such, they would agree with the last answer. Consistently, when the Rambam (Sefer HaMitzvos 217) asks why the Masechta is called Yevamos, when Chalitzah is also an option; he answers that it is because the Gemara (Yevamos 39b) states that yibum takes precedence over chalitzah. However, if, as the Tosafos Yeshanim’s second answer states, Seder Nashim begins with Yevamos because yibum is the first mitzvah to be mentioned for women, then it follows that the Masechta had to be called Yevamos rather than Chalitzah. But since the Rambam does not consider the woman’s involvement in yibum as her mitzvah, it was necessary for him to explain the Masechta’s name as stemming from yibum’s precedence. [ Pleasant Ridge Newsletter Vol. 16 # 33]

The Rambam asks the Tosfos Yeshanim’s question, as well and offers a different answer. He says that Kesuvos and Kidushin discuss the laws of marriage. Marriage is something that is left up to the willingness of the man and the women; Beis Din cannot force a man to marry a woman. Yibum is compelling; Beis Din informs the yavam that he must either perform a yibum or a chalitzah. It is appropriate to discuss the halachos that are compelling first.

Tosfos Yom Tov cites the Rambam in the fifteenth perek of Hilchos Ishus, who quotes the Gemora in Kidushin 29b, that one who reaches twenty years old and has not married is cursed by Hashem for he will be thinking about sin. It is implicit that there is no halacha that Beis Din can force someone to marry.

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Daf Yomi - Yevamos 2 - YEVAMOS, YIVUMOS OR YIVMOS

The Rambam in Sefer HaMitzvos (217) and the Chinuch state that this tractate is called Yevamos and not Chalitzos because the mitzvah of yibum takes precedence over the mitzvah of chalitzah.

Reb Yaakov Kamenetzky asks: This would be understandable if the name of the Mesechta would be Yivumos, referring to the act of yibum; however, the name is Yevamos, meaning the women who are Yevamos, in the same manner as the brother who is performing the yibum is called the yavam.

He concludes that perhaps the name of the Mesechta is actually Yivmos, referring to the halachos of yibum. This would explain the Rambam and the Chinuch’s question and answer.

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Daf Yomi - Yevamos 2 - Yibum with a Niddah

The Mishna lists fifteen women that exempt their co-wives and the co-wives of their co-wives from chalitzah and from yibum. One of them is his wife’s sister.

Tosfos asks: Why didn’t the Mishna include a case where the yevamah was a niddah at the time that she fell to yibum? She is forbidden to him at that time and he would be subject to the penalty of kares; wouldn’t there be a prohibition against performing a yibum with her even after she purifies herself?

Tosfos compares this case to the case listed in the Mishna; his wife’s sister. He cannot perform a yibum with her even if his wife would die (one is permitted to marry his wife’s sister after his wife dies). The explanation is: We consider the situation at the time when she falls to yibum; since at that time she was forbidden, she remains prohibited forever. Tosfos’ question is: Why don’t we apply the same logic to a woman who was a niddah at the time that she fell to yibum and just as she is forbidden at that time, she should remain prohibited even after she purifies herself?

Tosfos cites a Gemora in Pesachim (72b) which seems to indicate that a yavam who performs a yibum with a niddah had accomplished a mitzvah, and he has acquired her despite the fact that a transgression was committed.

(Tosfos answers this question by creating a distinction between his wife’s sister, who is only forbidden to him and a niddah, who is forbidden to everyone.)

The Acharonim ask: How can it be that the yavam has fulfilled the mitzvah of yibum by performing a yibum with a niddah; shouldn’t this be considered a mitzvah habaah b’aveirah, a mitzvah that is a result of an aveira that is performed? The positive commandment of yibum cannot override the negative transgression of engaging in relations with a niddah; this transgression is subject to the penalty of kares and cannot be overridden by a positive commandment. There are many Rishonim who maintain that one who performs a mitzvah and simultaneously commits an aveira does not fulfill the mitzvah at all.

Reb Elchonon Wasserman (Kovetz Heoros 11:1) answers: One does not fulfill the mitzvah by a case of mitzvah habaah b’aveirah when the mitzvah is merely an action, such as shaking a lulav or blowing a shofar; he cannot be credited with a mitzvah when that action was an aveira, as well. However, when the mitzvah is more than an action, but rather what the action accomplished, this principle is not applicable. If one circumcises a nine-day old baby on Shabbos, the milah is valid and he has fulfilled a mitzvah, despite the fact that a transgression was committed. This is because the mitzvah is that the child should be circumcised and that result was attained. The mitzvah of yibum is the acquisition of the yevamah through an act of yibum. While one who performs a yibum with a niddah has violated the prohibition of having relations with a niddah, he nevertheless has acquired the yevamah and thus has fulfilled the mitzvah of yibum.

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Daf Yomi - Yevamos 2 - Highlights

Introduction to Tractate Yevamos

It is written [Devarim 25: 5 – 10]: "If brothers dwell together, and one of them dies, and has no child, the wife of the dead shall not be married abroad to one not of his kin; her husbands' brother shall go into her, and take her to him to wife, and perform the duty of a husband's brother to her. And it shall be, that the firstborn that she bears shall succeed in the name of his brother that is dead, that his name be not blotted out of Israel. And if the man does not want to marry his brother's wife, then his brother's wife shall go up to the gate to the elders, and say: 'My husband's brother refuses to raise up to his brother a name in Israel; he will not perform the duty of a husband's brother to me.' Then the elders of his city shall call him, and speak to him; and if he stands, and says: 'I do not want to marry her'; then shall his brother's wife go up to him in the presence of the elders, and loose his shoe from off his foot, and spit before him; and she shall answer and say, 'So shall it be done to the man that does not build up his brother's house.' And his name shall be called in Israel, 'The house of him that had his shoe loosened'" (Deut. 25:5-10).

Rav Pinchas Kahati has an introduction to this tractate and to the details regarding the mitzvah of yibum. I present it to you in full. Here is the address where one can find the archives of any Mishna http://www.moreshet.net//oldsite/mishna/index.htm.

(1) The mitzvah of yibum applies only to brothers by the same father, and not to brothers by only the same mother, for it is written, "When brothers dwell with one another" – i.e., brothers who inherit with one another, thus excluding brothers who have only the same mother (Yev. 17b). Another opinion in the Gemara (ibid.) learns this law by tradition from the analogous use (gezerah shavah) of the word "brothers" referring to the sons of Jacob ("We are twelve brothers, sons of our father" – Gen. 42:32): just as the passage in Genesis refers to brothers by a common father and not by one mother, this passage also refers to brothers by the same father but not to brothers by the same mother. According to the Jerusalem Talmud, this law is implicit in the word "together" – "those who dwell in one house, excluding brothers by one mother (but different fathers), of whom one goes to the house of his father, and another goes to the house of his father."

(2) The phrase "and has no child [ben, lit., "son"] means, "and has no seed [zera]"; if, however, he does have descendants, even a daughter or a grandchild, the law of yibum does not apply to his widow.

(3) If the brother died without seed and left more than one wife (for formerly a Jew was permitted to be married simultaneously to several wives), one of his brothers marries by yibum, or submits to halitzah from, one of the wives, and thereby exempts all the rest from either yibum or halitzah, as it is written, "So shall it be done to the man that does not build up his brother's house," which it was understood to mean, he builds up one house but he does not build up two houses.

(4) Once a wife is exempt from the mitzvah of yibum, she becomes forbidden to marry her brother-in law under the prohibition of 'the brother's wife', of which it is written, "You shall not uncover the nakedness of your brother's wife" (Lev. 18:16). A baraita teaches: " 'The nakedness of your brother's wife' and 'her husband's brother shall go in to her' were stated in a single commandment" (Jer. Talmud, Ned. 3:2; Mekhilta; Sifri), i.e., the mitzvah of yibum alone exempts the yevamah from the prohibition of marrying the brother's wife, but the prohibition of the brother's wife applies to any woman who was released from the mitzvah of yibum.

(5) If the yevamah is prohibited to the yavam because of ervah (lit. "nakedness," i.e., family relationship), e.g., she is his daughter who had married his brother who died, or she is his wife's sister, then she is exempt from yibum. This is because it is written, "And you shall not take a woman to her sister, to be a rival to her, to uncover her nakedness beside the other" [aleha] (Lev. 18:18), and in the passage regarding yibum it is written, "her husband's brother shall go in to her [aleha]" – just as the latter is a case of mitzvah, so too is the former. Therefore the Torah stated, "And you shall not marry", i.e., even in order to perform the mitzvah of yibum it is prohibited to marry a woman and her sister; that yibum is prohibited in the other prohibited degrees of relationship is derived from the case of the wife's sister (Yev. 3b; 13a).

(6) Any woman who is exempted by Torah law from yibum is also exempt from halitzah, as it is written, "And if the man does not want to marry his brother's wife, then his brother's wife shall go up to the gate… and say : 'My husband's brother refuses to raise up to his brother a name in Israel…' and loose his shoe" (Deut. 25:7-9), from which it was understood that to whomever yibum applies, halitzah applies, and to whomever yibum does not apply, halitzah does not apply.

(7) If a man's brother died childless and left more than one wife, and one of them is prohibited to the yavam because of ervah, then just as the related woman is exempt from yibum and from halitzah, as was explained above, all the other wives of the dead man, who are called "her rivals" (see I Sam. 1:6), are similarly exempt from yibum and from halitzah, as it is written, "that does not build up his brother's house" – if he can build up the house in its entirety then he may build up part of a house, but he may not build up even part of a house which he cannot build up in it entirety.

(8) A widow who is prohibited due to ervah exempts not only her rivals from yibum and from halitzah, but also her rivals' rivals, and so on: e.g., Reuven died childless and left two wives, Leah and Hannah, and he had two brothers, Shimon and Levi, and Leah is the sister of Shimon's wife [Rahel]; in this case both yevamot, Leah and Hannah, are prohibited to Shimon: Leah, because she constitutes ervah for him, and Hannah, because she is the rival of a woman prohibited by ervah, as was explained above. Both of them are dependent upon Levi, however, for they are not related to him, and he must either marry by yibum or submit to halitzah from whicever one of them he wishes (Chart 1). If Levi married as his yevamah Hannah, i.e., the rival of the woman prohibited to his brother Shimon by ervah, and he (Levi) had another wife [Yehudit], and Levi also died childless, and his wives came before Shimon for yibum or halitzah – since Hannah is prohibited to him because of the ervah of her rival, then she also exempts her rival, i.e., Levi's second wife [Yehudit], from yibum and from halitzah. It follows from this that Leah, who is a woman prohibited to Shimon by ervah (since she is his wife's sister), exempts her rival and her rival's rival (Chart 2). This is also the law regarding her rival's rival's rival, ad infinitum. One view in the Gemara learns this from the passage, "And you shall not take a woman to her sister, to be a rival [li-tzror]" – since "li-tzror," and not "la-tzor" is written the Torah includes many rivals, i.e., the rival of the woman prohibited due to ervah, her rival's rival, her rival's rival's rival, and so on, all are exempt from yibum and from halitzah. Other authorities in the Gemara learn this law from other verses (see Yev. 8a). Rambam explains the reason for this law: in any case in which he has no zikah (the tie between a woman requiring yibum and the yavam) with her, she is prohibited to him forever on account of being his brother's wife; it follows from this that the rival of the woman prohibited by ervah is prohibited to him on account of ervah, and therefore she also exempts her rival (Hil. yibum 6:14-15); see also Rav Ashi's reason in the Gemara, Yev. 13a).

The Mishna states: Fifteen women exempt their co-wives and the co-wives of their co-wives from chalitzah (a ceremony by which the brother of the deceased man excuses himself from performing levirate marriage on the widow, which permits her to marry someone other than a brother of the deceased) and from yibum, until the end of the world. And these are the women: 1) his daughter, 2) and his daughter's daughter, 3) and his son's daughter, 4) his wife's daughter, 5) and her son's daughter, 6) and her daughter's daughter, 7) his mother-in-law, 8) and his mother-in-law's mother, 9) and his father-in-law's mother, 10) his maternal sister, 11) his mother's sister, 12) and his wife's sister, 13) his maternal brother’s wife, 14) the wife of his brother who was not in his world (this brother and the yavam were not alive at the same time), 15) and his daughter-in-law.

These women exempt their co-wives and the co-wives of their co-wives from chalitzah and from yibum, until the end of the world.

However, regarding all these women, if they died, or if they refused (a woman's annulment of a Rabinical marriage contracted for her in her minority), or if they were divorced, or if they were found to be an aylonis (an adult woman who did not develop any signs of female puberty and is incapable of bearing children), their co-wives are permitted. But you cannot say of his mother-in-law or his mother-in-law's mother or his father-in-law's mother that they were found to be an aylonis (since an aylonis cannot bear children) or that they refused (since only a minor can refuse).

How do they exempt their wives and co-wives? If his daughter or one of any of these arayos (a woman who it is prohibited to have relations with) was married to his brother, who had another wife, and he died childless, just as his daughter is exempt, so is her co-wife exempt.

If the co-wife of his daughter went and married to the second brother, who had another wife, and he died childless, just as his daughter's co-wife is exempt, so is her co wife’s co wife exempt, even if they are a hundred.

Courtesy of http://chavruta.tripod.com/

[Reuven, Shimon and Levi are brothers. Reuven has a daughter Penina, born out of wedlock. Shimon marries Penina. He has also married a non-related woman, named Chana. Shimon dies childless and his wives fall for yibum to Reuven and Levi. Reuven cannot perform yibum with Penina since she is his daughter. Chana, the co-wife is also exempt. Levi performs a yibum with Chana. Levi has another wife, named Malka. Levi dies childless and his wives fall for yibum to Reuven. The Mishna teaches us that Reuven cannot perform a yibum with Malka since she is the co-wife’s (Chana) co wife.]

How is it that if they died or if they refused, or if they were divorced, or if they were found to be an aylonis, their co-wives are permitted? If his daughter or any other one of these arayos was married to his brother, who had another wife, and his daughter died, or was divorced, and afterwards his brother died childless, her co-wife is permitted.

And whoever could have refused but did not refuse, her co-wifel performs chalitzah but may not marry him by yibum. (2a – 2b)

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