Gemara

(Mishnah): One is liable (for shaving his beard) only with a razor;

R. Eliezer obligates even with Melaket or Rehitani (tweezers or planing tools).

Question: How do Chachamim know that a Kohen is liable only for a razor?

Answer (Beraisa) Suggestion: "They (Kohanim) will not shave the corners of their beards." Perhaps a Kohen is liable even if he shaves with scissors!

Rejection: "V'Lo Sashchis (do not totally remove hairs)."

Suggestion: Perhaps one is liable even with a Melaket or Rehitani!

Rejection: "Lo Yegalechu (they will not shave)."

The Torah forbids shaving with Hashchasah, namely, with a razor.

41a - Question: Why did the Torah need to write (that a Metzora shaves) "Rosho" and "Zekano"? (Either suffices to teach that an Aseh overrides a Lav!)

Answer: Had it written only "Rosho", we would not learn that a Metzora must shave with a razor. Therefore, "Zekano" is also needed.

Makos 20a (Mishnah): One is liable for Pe'as ha'Rosh (the sideburns) one on each side, and for (corners of) the beard, two on each side and one in the middle;

R. Eliezer says, if he removed all of them at once, he is liable only once.

He is liable only with a razor; R. Eliezer obligates even with Melaket or Rehitani.

20b: Hakafas Pe'as ha'Rosh is evening the temple with the hairlines on the forehead and in back of the ears.

Rishonim

The Rif and Rosh (Makos 3b,4a-b and 3:5) bring the Mishnah and Beraisa.

Nimukei Yosef (4a (inside column) DH Zeh ha'Meshaveh): R. Yeshayah says that one is liable for Pe'as ha'Rosh only with a razor. We learn from a Gezeirah Shavah "Pe'as-Pe'as" from the beard. A Tosefta says that one is liable for Hakafas Pe'as ha'Rosh only with a razor. Also the Rambam says so.

Rebuttal (Rosh 2): The Tana'im discuss the beard. (Chachamim agree that) the sideburns do not require a razor (to be liable). The Gemara defined Hakafas Pe'as ha'Rosh to be evening the temple with the hairlines. It did not mention shaving with Hashchasah like it did regarding the beard. It mentioned only evening. Also, in Nazir, the Gemara needed "Zekano" to teach that a Metzora must shave with a razor. Why couldn't we learn this from "Rosho"? We must say that Hakafas Pe'as ha'Rosh is even without a razor, so "Rosho" would be needed to permit Gilu'ach Metzora even if a razor was not required. The Tosefta that obligates only with a razor means like (i.e. as close as) with a razor.

Defense (Ritva Makos 21a DH umi'Sugya): We learn that Hakafah is only with a razor from the beard. Only because it says "Zekano" to teach that Gilu'ach Metzora is with a razor, we know that also Hakafah is only with a razor.

Yere'im (336 DH Lo Sakifu): Toras Kohanim (Metzora 2:38) obligates for the sideburns with scissors like with a razor, but not for the beard. It refers to a Nazir.

Yam Shel Shlomo (Yevamos 12:8): The Rosh's proof from Nazir is solid. Even if the Tosefta argues, we do not follow it, for it was not taught in the academy of R. Chiya and R. Oshaya. The SMaG says that the Tosefta equates Gilu'ach of the sideburns and beard from a Hekesh. The Hekesh teaches only that in both cases the one whose hair is cut also transgresses. We do not learn about how one shaves, for the Torah specified Hashchasah only regarding the beard. Perhaps the sideburns are forbidden with a scissors even unlike a razor, for it evens the hairline. Only Melaket or Rehitani, which are not normally used for Hakafah, are excluded. 6. Rambam (Hilchos Avodah Zarah 12:6): Chachamim did not give a Shi'ur for the sideburns. We heard from our elders that one may not leave less than 40 hairs. One may remove them with scissors. It is forbidden only with a razor.

Rambam (7): One is liable for shaving the beard only with a razor, for it says "v'Lo Sashchis" - shaving that removes from the roots. Therefore, if he shaved with scissors he is exempt.

Perush ha'Mishnayos (Makos 20a): Melaket and Rehitani are tweezers or tongs that pluck the hair out, including the root. (Note: Tosfos (Avodah Zarah 74b Sof DH Darash) holds that both are planing tools. They do Hashchasah, but since people do not normally shave with them, it is not called Gilu'ach.)

Poskim

Shulchan Aruch (YD 181:3): One is liable (for Hakafas Pe'as ha'Rosh) only with a razor. Some forbid with scissors like with a razor. One should be concerned for their opinion.

Beis Yosef (DH Eino): The Gemara connotes that not only he is not liable with a scissors, rather, it is permitted l'Chatchilah, even very close like a razor. The Rambam learned from the Mishnah that one may cut the sideburns with a scissors. He holds that the Mishnah discusses the beard and sideburns. Tosfos and the Rosh hold that it discusses only the beard, but even they permit the sideburns with scissors if it is not very close. If not, the beard would be no different from the sideburns!

Beis Yosef (DH va'Adoni): Also the Tur, R. Yerucham and the Terumas ha'Deshen hold like the Rosh.

Shach (2): They forbid cutting close to the skin, like with a razor.

Shemesh Tzedakah (61, cited by R. Akiva Eiger): If a two-bladed scissors uproots the entire hair, this is utterly forbidden. I cannot fathom how Beis Hillel learns from Nazir 40a to forbid a salve. Gilu'ach is only with a razor!

Shulchan Aruch (10): One is liable for shaving the corners of the beard only with a razor. It is permitted with a scissors, even very close like a razor.

Beis Yosef (DH Eino): Even though the Rambam said 'one is not liable', he agrees that it is permitted l'Chatchilah. He merely cites the Mishnah. He permits even the sideburns l'Chatchilah, surely also the beard!

Rema: Nevertheless, when shaving with scissors we are careful to cut with the upper blade of the scissors, not the bottom, lest he cut entirely with the bottom, which is like a razor.

Source (Terumas ha'Deshen 295, cited in Beis Yosef DH va'Adoni): This concern is only when the scissors is very sharp.

Rema (ibid.): However, one need not be concerned about Tachas ha'Garon (between the chin and Adam's apple), since it is not the primary place of the corners.

Shach (7): The Bach says that even Tachas ha'Garon one may not cut with a scissors unless he leaves some hair. The Terumas ha'Deshen (who is stringent about scissors) is a stringency. All Poskim permit with scissors. We need not extend the stringency!