Chullin, Chapter 9, Mishnah 3. The chapter has been building a single principle in stages, and this mishnah brings it to its practical conclusion.
In the previous two mishnayot we learned that the skin of an animal is not treated as meat, neither for the tum'ah of food nor for the tum'ah of a neveilah. Skin is skin, not flesh. But there is an exception: when the skin is genuinely joined to the meat and functions as its shomer (its protector) or as its yad (its handle), it becomes a conduit. Tum'ah can travel through it in either direction.
Two examples show how this works. If the animal was slaughtered properly and is kosher meat, and something tamei comes into contact with the skin, the skin carries the tum'ah of food inward to the meat. If the animal is a neveilah, meaning it was not slaughtered properly, and a tahor person touches the skin, the skin carries the tum'ah of the neveilah outward to that person.
The Question of This Mishnah
All of that assumed the skin is sitting on the animal where it belongs. Our mishnah asks about the moment of transition: while a person is in the middle of stripping the hide off the carcass, at what point does the portion already peeled away lose its status as a handle, so that it no longer conducts tum'ah to the meat or from it?
The mishnah opens by sweeping away any distinctions in the animal itself: "Hamafshit babehemah uvachayah, batehorah uvateme'ah, badakah uvagasah," one who strips the hide, whether from a domesticated animal or a wild one, a kosher species or a non kosher species, a small animal or a large one. The rule that follows is the same in every case. What does make a difference is the purpose for which the hide is being removed, because the purpose determines the technique, and the technique determines what counts as the end of the job.
Skinning for a Leather Spread
"Leshatia'ach kedei achizah." If the intention is to use the hide as a leather spread, something like a leather mat or carpet, the skinner slits the hide lengthwise from head to tail and then peels it away toward both sides. Here the peeled portion remains a yad only until he has freed enough of it to take hold of with his hand, and that measure is two tefachim. Once he has peeled beyond that, the loosened part is no longer reckoned as part of the animal's skin at all. It is no longer a handle, and it can neither bring tum'ah to the meat nor carry tum'ah away from it.
Skinning for a Bottle
"Ulechemet ad sheyafshit et hachazeh." If he is removing the hide in order to fashion a skin bottle out of it, he does not slit it lengthwise. He folds the hide outward all the way around the neck and draws it down over the body toward the other end, keeping it whole. In this method the hide remains a handle until he has stripped away the animal's chest, which is the most difficult part of the body to skin.
Skinning from the Legs Upward
"Hamargil." Here too he wants a skin bottle, but he begins from the opposite direction: he folds the hide outward from the hind legs and pulls it down along the body all the way toward the neck. In this case, "kulo chibur latum'ah letamei uletamei," the entire hide remains joined for the purposes of tum'ah until he has removed all of it. As long as any of it is still attached, meat that is pure becomes tamei if a tamei person touches the hide, and a person who touches the hide becomes tamei if the animal is a neveilah.
The reason lies in the order of the work. When one skins from the tail toward the head, the chest, the hardest section, comes off at the very end. Until that final section has been freed, the hide is still considered part of the animal, and it still serves as its yad.
The Loose Skin at the Neck
In this last case, where the skinning runs from the tail toward the head, the chest is no longer the concluding stage. What, then, is the status of the hide once it has been drawn past the chest and is bunched around the neck? On this the mishnah records a machloket.
"O she'al hatzavar," regarding the loose skin remaining on the neck, "Rabbi Yochanan ben Nuri omer: eino chibur." Rabbi Yochanan ben Nuri holds that it is no longer considered joined, and it therefore conducts nothing.
"Vachachamim omrim: chibur ad sheyafshit et kulo." The Chachamim hold that it remains joined until he has literally stripped away the whole of it.