The status of a knife in which there are several notches is considered like that of a saw; and with regard to a knife in which there is only one notch, if it catches, the slaughter is unfit, but if it entangles [mesukhsekhet], the slaughter is fit. What are the circumstances of a notch that catches, and what are the circumstances of a notch that entangles? Rabbi Eliezer said: A notch that catches is one that has a sharp edge on two sides, while a notch that entangles is one that has a sharp edge on one side.

The Gemara challenges this explanation: What is different about a notch with a sharp edge on two sides, where the first edge [moresha] compromises the neck by removing the hide and the flesh, and the latter edge rips the simanim; in the case of a notch with a sharp edge on one side too, the sharp tip of the knife compromises the neck and the edge of the notch rips the simanim. The Gemara explains: The reference is to a notch that stands at the top of the knife, which begins the slaughter. The Gemara objects: Ultimately, when the knife goes in one direction it compromises the neck and when it comes back in the other direction it rips the simanim. The Gemara explains: The reference is to a case where he drew the knife backward and did not draw it forward.

Rava says: There are three types of notches in a knife. If the notch catches, one may not slaughter with it, and if he slaughtered, his slaughter is not valid. If the notch entangles, one may not slaughter with it ab initio; and if he slaughtered with it, his slaughter is valid after the fact. If the notch rises and falls in the knife and has no sharp edges, one may slaughter with it ab initio.

Rav Huna, son of Rav Neḥemya, said to Rav Ashi: You said to us in the name of Rava that if the notch entangles, the slaughter is not valid. But doesn’t Rava say: If the notch entangles, the slaughter is valid? Rav Ashi answers: This is not difficult. Here, where Rava says that the slaughter is not valid, is in a case where he drew the knife back and forth. There, where Rava says that the slaughter is valid, is in a case where he drew the knife backward and did not draw it forward.

Rav Aḥa, son of Rav Avya, said to Rav Ashi: If the knife was similar to an awn of grain [sasa], which is not perfectly smooth but does not have actual notches, what is the halakha? Rav Ashi said to him: Who will give us from the meat of an animal slaughtered with that knife, and we will eat it.

§ Rav Ḥisda says: From where is it derived that examination of a knife is an obligation by Torah law? It is derived from a verse, as it is stated with regard to Saul’s instructions to the people: “And slaughter with this and eat” (I Samuel 14:34), indicating that Saul gave them the knife only after ensuring that it was fit to slaughter their animals.

The Gemara asks: Isn’t it obvious that a knife must be examined before slaughter? Since were one to create a perforation in the gullet, the animal would be a tereifa, therefore the knife requires examination to prevent that situation. The Gemara answers: We are saying that a source for the halakha that one must show the knife to a Torah scholar for examination is needed. The Gemara asks: Is that an obligation by Torah law? But doesn’t Rabbi Yoḥanan say that the Sages said to show the knife to a Torah scholar only due to the requirement to show deference to the Torah scholar? The Gemara answers: Indeed, it is a requirement by rabbinic law, and the verse is cited as a mere support for that practice, not as a source.

The Gemara notes: In the West, Eretz Yisrael, they examine the knife in the sun to determine whether there is a notch. In Neharde’a they examine the knife with water. They would place the blade on the surface of the water, and if there was a notch, it would noticeably alter the surface of the water. Rav Sheshet would examine it with the tip of his tongue. Rav Aḥa bar Ya’akov would examine it with a strand of hair. He would pass the strand over the blade of the knife and if there was a notch, it would be caught in that notch.

In Sura they say: The knife consumes the flesh; let the flesh examine the knife. Since the concern is that the knife will rip the flesh during the slaughter, it should be examined by passing it on the tongue or the fingertip. Rav Pappa said: The knife requires examination on the flesh, and on the fingernail, and on the three sides of the knife, i.e., the blade and the two sides of the knife.

Ravina said to Rav Ashi: Rav Sama, son of Rav Mesharshiyya, said to us in your name that which you said to him in the name of Rava: The knife requires examination on the flesh, and on the fingernail, and on the three sides. Rav Ashi said to Ravina: On the flesh and on the fingernail I said, and on the three sides I did not say. There are those who say that Rav Ashi said to him: On the flesh and on the fingernail and on the three sides I said, and in the name of Rava I did not say.

Ravina and Rav Aḥa, son of Rava, were sitting before Rav Ashi. People brought a knife before Rav Ashi to examine it. Rav Ashi said to Rav Aḥa, son of Rava: Examine it. He examined it on the fingernail, and on the flesh, and on the three sides. Rav Ashi said to him: Well done, and Rav Kahana likewise said that this is the way to examine a knife.

Rav Yeimar said: Examination on the fingernail and on the flesh is necessary, and examination on the three sides is not necessary. Doesn’t Rabbi Zeira say that Shmuel says: If one heated a knife until it became white hot and slaughtered an animal with it, his slaughter is valid, as its sharp blade preceded the effect of its white heat; and it is difficult for us: But aren’t there the sides of the knife, which burn the throat and render the animal a tereifa? And we say: The area of the slaughter in the throat separates quickly after the incision, and the tissue on either side of the incision is not seared by the white hot blade. Here too, the area of slaughter separates quickly, and notches on the side of the knife do not come in contact with the simanim.

§ Rav Huna bar Rav Ketina says that Rabbi Shimon ben Lakish says that there are three deficiencies with the same measure, as follows: The deficiency of a bone in the Paschal offering, with regard to which it is written: “Neither shall you break a bone therein” (Exodus 12:46); the deficiency of an ear in a firstborn animal that renders it blemished and unfit for sacrifice, in which case a priest may slaughter it anywhere and eat it; and the deficiency that constitutes a blemish in other forms of sacrificial animals.

And Rav Ḥisda says: There is the deficiency of a knife as well. The Gemara asks: And the other amora, Rabbi Shimon ben Lakish, why does he not include the knife? The Gemara answers: He does not include it because he is not speaking with regard to non-sacred animals.

Rav Ḥisda continues: And with regard to all of these deficiencies, the measure of their deficiency is equivalent to the measure of deficiency that renders the altar unfit.