§ Rabbi Zeira says that Shmuel says: If one heated a knife until it became white hot [libben] and slaughtered an animal with it, his slaughter is valid, as cutting the relevant simanim with the knife’s sharp blade preceded the effect of its white heat. Had the effect of the heat preceded the cutting, the animal would have been rendered a tereifa, an animal with a wound that will cause it to die within twelve months, before the slaughter was completed, by searing the windpipe and the gullet. The Gemara asks: But aren’t there the sides of the knife, which burn the throat and render the animal a tereifa? The Gemara answers: The area of the slaughter in the throat parts immediately after the incision, and the tissue on either side of the incision is not seared by the white-hot blade.

A dilemma was raised before the Sages: If one heated a skewer [shappud] until it became white hot and struck a person with it, and after the wound healed a leprous mark developed, is that mark adjudged as a leprous boil or is it adjudged as a leprous burn?

What is the practical difference whether it is adjudged a boil or a burn? The difference is for that which is taught in a baraita: Both a leprous boil and a leprous burn become impure during one week of quarantine with two symptoms: With white hair that grows in the leprous mark and with spreading of the leprous mark. And why did the verse divide them into two separate passages even though their halakhic status is the same? The verse divided them to say that they do not join together to constitute the requisite measure of impure leprous marks. Rather, there is impurity only if the boil or the burn constitutes that measure individually.

And it is taught in a baraita: Which wound is a boil and which is a burn? If one was struck with wood, with a stone, with pomace, with the hot springs of Tiberias, or with any item that is not heated by fire, a phrase that serves to include lead that was mined from its source in the ground, which is occasionally hot enough to burn a person, this impression left on the skin is a boil. And which wound is a burn? If one was burned with a coal, with hot ashes, with boiling limestone, with boiling gypsum [begippesit], or with any item that is heated by fire, a phrase that serves to include water heated by fire, this impression left on the skin is a burn.

And it is taught in a baraita: If there is a boil and a burn on the same place on the skin and a leprous mark developed, the later wound determines the nature of the leprosy. Therefore, if the boil preceded the burn, the burn nullifies the boil and the mark is a leprous burn. And if the burn preceded the boil, the boil nullifies the burn and the mark is a leprous boil.

And here, where the dilemma was raised whether the mark that develops from being struck with a hot skewer is a boil or a burn, what are the circumstances? It is a case where initially there was a boil half the size of a split bean on the person’s skin, and one heated a skewer until it became white hot and struck him with it, and another mark half the size of a split bean emerged on the skin there.

The Gemara clarifies the dilemma: What is the halakha? Does the effect of the blow come first and then the effect of the heat comes and nullifies the effect of the blow, and it is a half-measure boil and a half-measure burn and they do not join together to constitute a full measure? Or perhaps the effect of the heat comes first and then the effect of the blow comes and nullifies the effect of the heat, and it is a half-measure boil and a half-measure boil and they join together.

The Gemara suggests: Come and hear a resolution to the dilemma from that which Rabbi Zeira says that Shmuel says: If one heated a knife until it became white hot and slaughtered an animal with it, his slaughter is valid, as cutting the relevant simanim with the knife’s sharp blade preceded the effect of its white heat. Apparently, the effect of the blow comes first. The Gemara rejects that proof: Cutting with a sharp blade is different from striking with a blunt object, and only in the case of a blade does the cut precede the effect of the heat.

The Gemara suggests: Come and hear a resolution to the dilemma from a baraita: If one heated a skewer until it became white hot and struck a person with it and after the wound healed a leprous mark developed, that mark is adjudged as a leprous burn caused by fire. Apparently, the effect of the blow precedes the effect of the burn. The Gemara rejects that proof: There too, the reference is to a case where he stabbed the skin with the skewer, which is the same as cutting with a sharp blade.

§ Rav Naḥman says that Rabba bar Avuh says: With regard to a knife used for idol worship, it is permitted to slaughter an animal with it, but it is prohibited to cut meat with it. It is permitted to slaughter an animal with it because slaughtering it is a destructive action vis-à-vis the animal, which is worth more when it is alive. But it is prohibited to cut meat with it, because once the animal is slaughtered, cutting it is a constructive action that renders the meat manageable.

Rava said: There are times when it is prohibited for one who slaughters an animal to use a knife used for idol worship, e.g., in the case of an animal that is in danger, meaning that it is about to die. If he does not slaughter the animal it would become an unslaughtered carcass and depreciate in value. And there are times when it is permitted for one who cuts meat to use a knife of idol worship, e.g., in the case of an animal whose thighs are intended to be sent as a gift to a person of stature. Cutting it into pieces would render it unfit for this purpose, thereby diminishing its value.

The Gemara challenges: And derive that it is prohibited to use a knife used for idol worship, not because benefit from it is prohibited, but due to the residue of fat of forbidden carcasses on the knife.