(Mishnah): Three people shave, and it is a Mitzvah to shave: a Nazir, a Metzora, and Leviyim (when they were chosen to serve in the Mishkan) All of them, if they shaved without a Ta'ar, or they left two hairs, they did not do anything (it is not a Mitzvah at all).

(R. Elazar): The Mishnah discusses a Nazir Tamei, but a Nazir Tahor, once he shaved the majority of his head, even without a razor, he was Yotzei.

Question (R. Ami, against R. Elazar): The Torah specified a razor only for a Nazir Tahor! "Ta'ar Lo Yavo Al Rosho Ad Melos ha'Yamim" implies that after finishing the days, he needs [specifically] a razor!

Answer: Perhaps [R. Elazar] said [that the Mishnah must discuss] a Nazir Tamei due to [the law of] two hairs (if he left two hairs, he did nothing; if he brought Korbanos, they are Pasul. However, if it discussed a Nazir Tahor, he could shave what remains!)

Question: Why not [say that 'if he left two hairs, he did nothing' applies to] a Nazir Tahor?

Answer: A Nazir Tahor shaves after Zerikah. Since he was Mekadesh all his Nezirus hair through blood [of a Korban], it is as if his hair fell out (so we are not concerned how he shaves).

R. Yosi (to R. Yakov bar Acha): Do you remember that we were learning Nazir, and we said 'there is no difference between scissors and a razor regarding a Nazir Tamei (since he shaves merely to remove Tamei hair) and [now] R. Elazar said that the Mishnah discusses a Nazir Tamei?! (I.e. now they were learning Nega'im. R. Elazar said that the Mishnah discusses a Nazir Tamei due to two hairs, so also the Reisha (a razor is Me'akev) applies to a Nazir Tamei, unlike we thought. We explained this like SEFER NIR.)

NOTE: SEFER NIR concluded 'also a Nazir Tamei needs a razor.' It seems that R. Yosi holds like R. Ami's question, that all the more so a Nazir Tahor needs a razor. However, R. Elazar disagrees, for he said that a Nazir Tahor is Yotzei even without a razor. (PF)

Question: You say that for a Nazir Tahor, the majority of his head is Me'akev. If he shaved a third, and he did not suffice to shave [more] before it all grew, does he shave the rest (i.e. more, so that in all he shave the majority) and this suffices? Or, must he shave all (i.e. a majority now, without relying on the first third)?

Question: You say that for a Nazir Tamei, two hairs are Me'akev. Correspondingly in a Nazir Tahor, two hairs are not Me'akev; [do we say that] two hairs do not cancel?

Answer (R. Yosi bei R. Bun): Yes (two hairs do not cancel).

Support (Tosefta 4:3 - R. Shimon ben Yehudah citing R. Shimon): Just like two hairs are Me'akev, two hairs cancel. (The Reisha (Chachamim) says that only the majority cancels.)

Question (R. Yirmeyah): If he shaved all [his head] and left two hairs, and they were enough to bend the end to the root (the minimum Shi'ur to be considered shaving) twice, and he shaved them once (i.e. cut them to half the size) - since he shaved the amount of a Siman (of maturity), he was Yotzei? Or, since he left the Shi'ur for a Siman, he was not Yotzei? (He discusses a Nazir Tamei. We learn from a Nazir Tahor to require a razor. Perhaps this is only for the majority of the head, like Nazir Tahor. We explained all this like SEFER NIR.)