Thirty Complete Days

The Mishna (Daf Yomi: Nazir 16a) had stated: If one says, “I am hereby a nazir for thirty days,” and he shaves his head on the thirtieth day, he has not discharged his obligation.

According to Bar Pada, this halacha is understandable. For since he explicitly said that he will be a nazir for thirty days, his nezirus is for thirty days, and Bar Pada does not hold that a partial day is regarded as a complete day. This is why he would be required to take his haircut on the thirty-first day. However, according to Rav Masna, his haircut should be valid, for he holds that part of a day is like the entire day!

The Gemora (5b) answered: The Mishna is referring to a case where he said, “I am hereby a nazir for thirty complete days.” The Rosh explains that everyone would agree that a partial day is not regarded as a day in a case where he explicitly said “complete days.”

Tosfos explains differently: One who says, “I am hereby a nazir for thirty days” is regarded as if he said, “I am hereby a nazir for thirty complete days.” The reason is as follows: Since it has been established that a standard nezirus is for thirty days, why would he say “for thirty days”? It would have been sufficient for him to have said, “I am hereby a nazir”! By the fact that he added, “for thirty days,” this indicates that he wishes to be a nazir for thirty complete days.

The Keren Orah and the Brisker Rav explain the Gemora according to the Rambam: We do not use the principle of “a partial day is regarded as an entire day” in any case where the person mentions a specific number. If he accepts nezirus upon himself without specifying a number, we would say that a partial day is regarded as an entire day. However, in this case, he specified an amount, and therefore, the principle is not applicable.