What is the connection between the shekalim and kilayim?
The Satmar Rebbe used to say: It is well known that the obligation to donate a half-shekel to the Beis Hamikdosh and not a whole shekel implies that a person is not complete by himself. He must join together with other Jews and only then will he be considered a whole person.
At the same time, one must be wary about bonding with a wicked person. It is written in Avos d’Reb Nosson (30:3): One who unites with an evil person even if he himself does not engage in the same manner as him will receive punishment similar to the retribution that will be administered to the wicked person. One who unites with a righteous person even if he himself does not perform virtuous acts will receive reward similar to the reward of the righteous person.
The proclamation and inspecting of the kilayim is to promote this concept. The Torah prohibits various mixtures of crops from growing together, so too, one must be careful as to whom his friends are.
Rabbi A. Leib Scheinbaum here quotes from Horav Yosef Chaim Sonnenfeld. He explains that a person must strive to cultivate relationships. As the Tanna says in Pirkei Avos 1:6, Knei lecha chaver, "Acquire for yourself a friend." One who lives as an individual lives as an incomplete person. He is missing a part of himself. Nonetheless, one must maintain criteria with regard to his relationships. He must be sure to associate only with those people who are appropriate. Just as certain admixtures of crops are forbidden, so, too, is it unwise to develop an affiliation with people of questionable or incompatible character. The positive effect of a good friend - and, conversely, the negative effect of a bad friend - cannot be emphasized enough.
Dr. Nosson Chayim Leff http://www.torah.org/advanced/sfas-emes/5764/shekalim.html cites a Sfas Emes who offers a different explanation. "On the first day of Adar, we inform people about their obligation to donate a half shekel to the Beis HaMikdosh and about kilayim (that is, the obligation, when planting one's field, to avoid mixing seeds of different plants, such as grapes and wheat)."
The Sfas Emes poses a basic question: Why were these announcements made specifically in the month of Adar? The Sfas Emes answers that the month of Adar resembles the month of Elul in certain important ways. We know that Elul is the month before the end of one year and the beginning of a new year that begins with Rosh Hashana. Thus its position as a potential turning point in our lives makes Elul a propitious time for doing teshuva, for repenting. So, too, the Sfas Emes tells us, the month of Adar immediately precedes the new year that begins in Nisan. Thus, Adar is also well placed for a person to look inside himself and do teshuva. Because of its importance, Adar is a good time for making the key announcements mentioned in the Mishna.
But, notes the Sfas Emes, there is an important difference between teshuva in Adar and teshuva in Elul. In Elul, we do teshuva from yirah (fear or a sense of awe). By contrast, in Adar, we can more easily do teshuva out of a sense of love (ahava) for HaShem. Indeed, that is why we experience heightened joy? simcha - in Adar. When Adar comes, our expansiveness and good feeling toward HaShem increase.
That is the reason for our obligation to donate half a shekel to the Beis HaMikdosh. Obviously HaShem does not need our donations. What He wants is to give us the opportunity to awaken our good feelings and dedication toward Him.
(Note, incidentally, that the Sfas Emes has just given us a whole new perspective on giving tzedaka. The conventional view sees us giving tzedaka because of our commitment to observe mitzvos. Ultimately, love for HaShem may enter the process. But that happens only if we work on ourselves diligently enough to do the mitzva not by rote and or out of social pressure but rather because of our love for HaShem. By contrast, the Sfas Emes sees the process as beginning from our love and good feelings to HaShem.)
Every Jew has within him a latent devotion to HaShem. What we need is an activity to express that devotion. The obligation to give the half shekel to the Beis Hamikdosh provides such an opportunity. And because Adar gives us an opportunity to express that love for HaShem, we feel more joy!
At this point, the Sfas Emes injects a note of severe caution into the ma'amar by citing a dvar Torah from his grandfather, the Chidushei Harim. The pasuk in Shir HaShirim (7:2) says: "Mah yafu pe'ahmayich bane'alim, bas nadiv." (ArtScroll: "But your footsteps were so lovely when shod in pilgrim's sandals, O daughter of nobles."). The Chidushei HaRim read this pasuk in the following non-pshat manner: The generosity and expansiveness of spirit (he is reading "pe'ahmahyich as "pulse rate," i.e., "spirit") of the Jewish people as the descendants of Avraham Avinu (whose great chesed and magnanimity entitled him to the sobriquet "the Nadiv," i.e., the "benefactor") is so great that it must be locked up ("min'al" = lock). That is, this love can be so overpowering that it has to be watched and controlled lest it go outside, i.e., be misdirected. (Anyone familiar with the devotion and love that too many Jews in Russia and Poland harbored for communism will concur in this comment of the Chidushei HaRim.)
The Sfas Emes continues, addressing a question that may have bothered you earlier. The Mishna quoted above juxtaposes two things. First, it specifies awakening people’s hearts to nedivus, expansiveness. The Mishna conveys his message by requiring all of us to make a donation to the Beis Hamikdosh. Then the Mishna warns us to be careful to avoid kilayim. What is the connection between these two items in the Mishna? The Sfas Emes answers this question by offering us a non-pshat reading of the word 'kilayim'. He reads the word as an allusion to "locking up" (as in "beis ha'kela" = prison). People must be warned to be careful with their idealism and generosity.
The Sfas Emes concludes: Every year when we read the parsha of Shekalim, our hearts are awakened to give all to HaShem. Unfortunately, we do not have the Beis HaMikdosh and thus cannot give our all as an offering. But in any case, HaShem's love for us is awakened, and we can do teshuva with simcha.
I saw another explanation offered by the members of the St. Louis Kollel. http://stlkollel.com/bits/5757/vayakhel.txt The Talmud in Megillah 13b states in the name of Rish Lakish, "It was well known beforehand to Him at Whose word the world came into being, that Haman would one day pay shekels for the destruction of Israel. Therefore, he anticipated his shekels with those of Israel, and so, we have learned "on the first of Adar, a proclamation is made regarding the shekalim and the mixed seeds (kilayim).
The Shem MiShmuel explains the connection between the shekels of Bnei Yisroel and those of Haman. He cites his father who says that the mitzvah of shekalim alludes to the giving over of a person's ten powers for the love of Hashem. (See Gur Aryeh, beginning of Parshas Terumah.) The shekel weighed ten gairah, an allusion to these ten powers a person possesses. It was from silver, kesef, which comes from the word nichsapha, desire or longing. The giving over the silver shekel represented the desire to give over, in love these ten powers. Haman's main intent was not to merely wipe out Bnei Yisroel for the sake of eradicating them. Rather, his intent was that the seventy nations of the world should take over Bnei Yisroel's role in the world and replace them in their special relationship to Hashem. His shekalim therefore, were very similar in intent to Beni Yisroel's. He handed over a fortune to Achashverosh in order to bring about the replacement of Bnei Yisroel by the 70 nations. His shekalim were also given over, as if to say, in love of Hashem.
"Shekalim" comes from the word "to weigh." Hashem weighed the pure intent of Bnei Yisroel, in contrast to Haman's intent that was not completely pure. His underlying intent was really to destroy Yisroel, and it was only clothed with the intent of the 70 nations gaining a closer relationship with Hashem. This explains the connection in the Mishna between shekalim and the prohibition to mix seeds (kilayim).
The shekalim have to be pure without any mixed intentions. Our avoda during Adar is to purify our intentions that we should truly desire to give over of ourselves all our powers for Hashem's service, without any selfishness.