Finding the Nape and the Hard Service of Pinching the Bird

"From opposite its nape" (Leviticus 5:8). "Opposite" means the place that faces the nape. And so it says, "and he dwells opposite me" (Numbers 22:5), and it says, "for they have turned their nape to me and not their face" (Jeremiah 2:27). Why the second proof? Lest you say, I do not know where the nape itself is, so how shall I know where the place opposite it is? Come and hear: "they have turned their nape to me and not their face," from which we learn that the nape is on the side opposite the face. The school of Rabbi Hiyya said: the manner of pinching is that he turns the windpipe and gullet around to the back of the nape and then pinches. Some say he may also turn them; others say he must specifically turn them; and it stands to reason like the one who says he may also turn them. Rabbi Shimon ben Lakish said in the name of Rabbi Elazar ben Pedat in the name of Rabbi Elazar ben Shammua: I have heard that in the bird sin offering one may sever, and what is the meaning of "he shall not divide it" - that he need not divide it. Rav Acha son of Rava said to Rav Ashi: if so, regarding the pit, where it is written, "and he does not cover it, and an ox falls in" (Exodus 21:33), here too should it mean that he need not cover it? He said to him: there, since it is written, "the owner of the pit shall pay," we infer by implication that covering is required; but here, since it is already written "and he shall offer it" (Leviticus 1:15) and Scripture distinguished between the bird sin offering and the bird burnt offering, why do I need "he shall not divide"? Learn from this that he need not divide. "And he shall not divide" - yet if he did divide, it is invalid.