Gemara

Question (Rav Yosef): What is the law of hair of a Tzadekes of an Ir ha'Nidachas?

Objection (Rava): You assume that hair of a Resha'ah must surely be destroyed. "Tikbotz... v'Sorafta" - we burn only what is ready to be gathered and burned, and not hair (or anything else) that must first be detached! Rather, we may ask about a wig of a Tzadekes of the city.

Question: If it attached to her, it is like herself!

Answer: The case is, it is hanging on a peg;

Erchin 7b (Mishnah): If a woman was executed (we may benefit from her hair).

Question: Why is this permitted? One may not benefit from a Mes!

Answer #1 (Rav): It is not her hair. It is a wig.

Question: R. Yosi b'Rebbi Chanina never resolved this! (This Gemara holds that Rava explained that R. Yosi asked about a wig.)

Answer: R. Yosi asked about a wig that she was not wearing.

Objection (and Answer #2 - Rav Nachman bar Yitzchak): Presumably, the case of her hair is like (the other case in the Mishnah), i.e. an animal's hair, i.e. its own hair! Rather, one may benefit from her until she dies (and death does not affect her hair, so it does not forbid it).

Berachos 5b: R. Yochanan would say (to console mourners) 'this is a bone from my tenth son.'

Mo'ed Katan 8b (Beraisa): We do all needs of a Mes (during the Mo'ed). We cut the hair...

Nazir 51a (Rabah bar bar Chanah): If the hair was cut and buried with the Mes, it is Galgalin to the Mes (it is considered a foreign decaying matter with the Mes, so the Rekev (corrosion) of the Mes is Tahor).

(Mishnah): Every part of a Mes is Tamei, except for the teeth, hair and nails. When they are attached, even these are Tamei.

Question (Chizkiyah): Are hair and nails of a Mes destined to be cut considered as if they are already cut, or are they considered to be attached? (This determines whether or not they are Tamei, or whether they cause that the Rekev (corrosion) of the Mes is not Tamei (for something else decayed with the Mes).

Sanhedrin 46b - Question: Is the reason for burial to avoid disgrace (of a rotting corpse), or for atonement?

The answer teaches about one who asked (before he died) not to be buried: if we are concerned for disgrace, we do not comply. If it is for atonement, he shows that he does not want it (and we honor his request).

Shabbos 93b (Mishnah): If one takes a k'Zayis of a Mes to Reshus ha'Rabim, he is liable;

R. Shimon exempts.

Rishonim

Rif and Rosh (Mo'ed Katan 3b and 1:14): We do all needs of a Mes (during the Mo'ed). We cut the hair...

Rambam (Hilchos Evel 4:1): We cut off a Mes' hair.

Rambam (Hilchos Tum'as Mes 3:13): If one touches hair or nails of a Mes that are destined to be cut off, it is a Safek if he becomes Tamei.

Rashbam (116a DH Dein): R. Yochanan kept a tooth from his son. A tooth of a Mes is not Metamei.

Poskim

Shulchan Aruch (YD 352:4): We cut off a Mes' hair.

Rema: We also cut the nails.

Prishah (7) and Chidushei Hagahos (1): The text of the Tur (who cites the Rambam) should say 'we cut the hair and nails.'

Gesher ha'Chayim (1:9:3, footnote 4): Here (in Eretz Yisrael), the custom is not to cut the hair or nails of a Mes.

Shulchan Aruch (OC 526:4): On Yom Tov Sheni, one may cut myrtle for a Mes, cut its hair...

Suggestion: If a Mes had a false tooth from a Neveilah, perhaps we should burn it, lest the grave be plowed, and one will find the tooth and think that it is Metamei and burn Terumah due to it! Even though now we are Tamei, we still wash for bread due to Terumah!

Answer (Panim Me'iros 3:33): We need not be concerned for this. It is uncommon for a grave to be plowed. Also, a tooth has no Tum'ah (Nazir 51). There is no more concerned for a false tooth than for real teeth! I say that it is better to bury the tooth with the Mes, than to remove it and risk forbidden benefit from it.

Birkei Yosef (Yosef Ometz 30): A man was saving his teeth that fell out to be buried with him, and was anguished that he lost one. I say that even great people are not concerned for this. R. Yochanan kept a tooth from his son! One could reject this proof. I did hear that people in Eretz Yisrael are particular about this. Ma'avar Yabok mentions that he saw people conduct like this, without comment (that one should do so).

Gesher ha'Chayim (1:16:2:1,2): The body was like the margin or case of Kedushah (the Neshamah), so any part of it so it requires Genizah (burial). Burial of any part of a Mes shows anticipation of Techiyas ha'Mesim. Teeth that separated after death must be buried, because one may not benefit from them.

Tosfos Yom Tov (Shabbos 10:5 DH v'Chen): The Mishnah obligates one who takes to Reshus ha'Rabim a k'Zayis of a Mes. Perhaps the Mitzvah to bury is only if there is at least a k'Zayis.

Rebuttal (Mishneh l'Melech Hilchos Evel 14:21, DH Asher): The Yerushalmi (Nazir 7:1) obligates burial only if the head and majority are intact. Perhaps the Mishnah discusses a Mes Nochri. A k'Zayis is useful to feed to a dog.

Kol Mevaser (1:70): Since R. Yochanan did not bury the bone, we must say like the Tosfos Yom Tov that less than a k'Zayis need not be buried. The Mishneh l'Melech admits that when a full Mes is found, we must return to bury a limb, like the Yerushalmi and Shulchan Aruch (YD 374:2) say. Perhaps this refers only to a limb that is Metamei.

Kol Mevaser (1:70): It is clear from Shulchan Aruch 526:4 and Nazir 51a that one need not bury hair of a Mes with the Mes. Surely this is like the opinion (Erchin 7b) that permits benefit from it. Rav forbids, but surely he agrees that we cut the hair, like the Beraisa in Mo'ed Katan. We must say that even though hair is forbidden, for it is not worse than shrouds, it is not like the body, and "you will bury it" does not apply to it. This is like the Mishneh l'Melech, who obligates burial only if the head and majority are here. Even if one may not benefit from it, he need not bury it. He may cast it to the sea, or grind it up and cast it to the wind. The Tosfos Yom Tov obligates burying a k'Zayis of a Mes. He agrees that hair is unlike the body, and it need not be buried. Perhaps after we cut the hair of a Mes, we bury it with the Mes. However, if so, the Poskim would have said so. Perhaps the opinion that forbids the hair because it is like the body, would obligate burying the hair when he finds the head and majority. However, it says "bury, and do not be Metamei the land." Since hair, teeth and nails are not Metamei (Nazir 51b), one need not bury them. This is explains why we cut the hair and nails, and why R. Yochanan kept a tooth of his son. The Rashbam, Aruch and R. Gershom explain that a tooth is not Metamei, i.e. and therefore, he did not need to bury it. Rashi (Berachos 5b) explains that the bone was less than a barley seed, and had no Tum'ah. Perhaps this is like the Tosfos Yom Tov, who obligates only for a Shi'ur of Tum'ah. The Tosfos Yom Tov himself was unsure. One must bury a bone the size of a barley seed, even though it has no Tum'as Ohel, just like one must bury Nochrim, who have no Tum'as Ohel. Rav Nisim Gaon (Berachos 5b) explains that R. Yochanan's tenth son fell into a boiling cauldron, and all his flesh melted, and only bones remained. Since the head and majority did not remain, there was no Mitzvah to bury even bones with a Shi'ur Tum'ah.

Mishneh Halachos (16:113): In some places, the custom is to cast baby teeth in a mousehole. This is because the entire body, including teeth, must be buried. Even though the Noda b'Yehudah held that a limb need not be buried, he came to his son in a dream and asked him to bring his tooth from a certain place to his grave. The son was astounded to find the tooth there.