are the ziva of a zav, and his spittle, and his semen, and his urine, and the blood of a menstruating woman, all of which impart impurity both by touching and by carrying.

The Gemara questions this assertion: But perhaps here too the reason for the severity of ritual impurity of the semen is indeed because it is impossible for it to emerge without small drops of ziva accompanying it, but it is not due to the impurity of the semen itself. The Gemara rejects this opinion: If that would be so, let the tanna of the mishna teach it in the list of bodily fluids along with, meaning list it immediately following, his ziva. What is different about semen that he teaches it along with: His spittle? Rather, it is because its halakha comes from, i.e., it is derived from, that of his spittle, and therefore the semen itself imparts impurity by carrying, even if there would not be small drops of ziva accompanying it.

The Gemara returns to the primary discussion concerning the principle: It is sufficient for the conclusion that emerges from an a fortiori inference to be like its source. Rav Aḥa of Difti said to Ravina: But there is this tanna who does not apply the principle: It is sufficient, at all, even though such application would not refute the entire a fortiori inference. As it is taught in a baraita: From where is it derived that a thick mat can contract ritual impurity from a corpse? It is a logical derivation based on an a fortiori inference: And just as small clay vessels, into which even a finger cannot be inserted because of their narrow opening and which remain ritually pure despite contact with a zav, nevertheless become impure if present under one roof with a corpse, then is it not right that a mat, which can become impure due to contact with a zav, will similarly become impure if present under one roof with a corpse?

And the tanna cites this a fortiori inference both to derive the halakha that the mat becomes ritually impure with impurity that lasts until nightfall, as it would if it were to come into contact with a zav, and to derive that the mat becomes ritually impure with impurity that lasts for seven days, as would any vessel that contracted ritual impurity from a corpse. And why does he do so? Say instead that the a fortiori inference is effective in deriving the halakha that the mat can contract ritual impurity from a corpse, but only with regard to rendering it impure until nightfall, and also say that the principle: It is sufficient, is effective by limiting the scope of the a fortiori inference to exclude the possibility that the mat would be rendered impure for seven days.

Ravina said to Rav Aḥa: This question was already raised by Rav Naḥman bar Zekharya to Abaye, and Abaye said to him in response: This tanna does not derive the halakha with regard to the mat through an a fortiori inference from the case of a zav. Rather, he derives it from the halakha of a mat that came into contact with the carcass of a creeping animal, and this is what he is saying: The first derivation is as follows: From where is it derived that a mat is susceptible to impurity imparted by the carcass of a creeping animal? And it is a logical derivation based on an a fortiori inference: And just as small vessels, which remain pure despite contact with a zav, nevertheless become impure from contact with the carcass of a creeping animal, is it not right that a mat, which becomes impure from the impurity of a zav, will likewise become impure from contact with the carcass of a creeping animal?

The second derivation is as follows: But from where is it derived that a mat contracts impurity from a corpse? It is derived through a verbal analogy. With regard to impurity imparted by the carcass of a creeping animal, it is stated: “Or a garment or leather” (Leviticus 11:32), and with regard to impurity imparted by a corpse it is stated: “A garment, or anything made of leather” (Numbers 31:20). Just as with regard to the terms “garment” and “leather” stated with regard to a creeping animal, a mat becomes impure from it, so too with regard to the terms “garment” and “leather” stated with regard to a corpse, a mat becomes impure from it.

The Gemara notes: It must be that the words “garment” and “leather” are free, i.e., those terms must be extraneous in their contexts, and the Torah included them for the express purpose of establishing the verbal analogy, as a verbal analogy that is based on otherwise extraneous terms cannot be logically refuted. Because if these terms are not free, the verbal analogy can be refuted: What is unique about a creeping animal? It is unique in that it renders items impure even by means of contact with a lentil-bulk of a creeping animal. Shall you also say that this is the case with regard to a corpse, whose halakhot are less strict in that it does not render items impure by means of contact with a lentil-bulk of a corpse but rather by means of contact with an olive-bulk? Unless the terms are free, the analogy can be refuted.

The Gemara affirms: Indeed, the terms are free. The Gemara proves that the terms “garment” and “leather” are extraneous in their context. Now, since ritual impurity imparted by contact with a creeping animal is juxtaposed to ritual impurity imparted by contact with semen, as it is written: “And one who comes into contact with anyone impure with impurity imparted by a corpse, or a man from whom semen is emitted” (Leviticus 22:4), and juxtaposed to that verse is the verse: “Or a man who touches any creeping animal which makes him impure, or a person who may make him impure with any impurity that he has” (Leviticus 22:5); and it is written with regard to the impurity of semen: “And every garment and all leather that has semen on it shall be washed with water and will be impure until evening” (Leviticus 15:17), since the verses appear next to each other, the halakhot of each can be derived from the other.

Consequently, why do I need the words “garment” and “leather” that the Merciful One wrote with regard to a creeping animal? The relevant halakha could be derived from the halakhot of seminal impurity. Consequently, learn from it that “garment” and “leather” were mentioned to render them free, i.e., extraneous, but the Torah included them for the express purpose of establishing the verbal analogy.

The Gemara comments: And still, the terms “garment” and “leather” are free only from one side of the verbal analogy, because although the terms “garment” and “leather,” stated with regard to ritual impurity imparted by a creeping animal, are extraneous in their context, as the relevant halakha could have been derived in another manner, those terms stated with regard to impurity imparted by a corpse are not extraneous in their context. This works out well according to the one who says that with regard to a verbal analogy that is free from only one side, one can derive from it and one cannot refute it logically; it is well. But according to the one who says that one can derive a halakha from a verbal analogy of this kind and one can also refute it logically, what can be said? It has already been established that the carcass of a creeping animal is stricter in some senses than a corpse.

The Gemara answers: The terms “garment” and “leather,” as stated with regard to impurity imparted by a corpse, are also free. Since the impurity of a corpse is juxtaposed with that of semen, as it is written: “And one who comes into contact with anyone impure with impurity imparted by a corpse, or a man from whom semen is emitted” (Leviticus 22:4), and it is written with regard to semen: “And every garment and all leather that has semen on it” (Leviticus 15:17), why do I need the terms “garment” and “leather” that the Merciful One wrote with regard to impurity imparted by a corpse? Learn from it that they are mentioned in order to render them free, and therefore it is free from both sides.

The Gemara questions this from a different angle: This works out well according to the one who says: Infer the halakha from it and interpret it according to its new place. This would mean that the halakha that a mat becomes impure from a corpse is derived from the halakha that a mat becomes impure from semen, but the details of that impurity, i.e., the length of the time it is impure, are interpreted according to the halakhot of impurity imparted by a corpse, for seven days. But according to the one who says: Infer the halakha from it and infer the details of the halakha from it as well, which would mean that the details of the impurity would also be interpreted according to the halakhot of impurity imparted by semen, what can be said? According to the latter opinion, it should be concluded that just as the impurity imparted to a mat by the carcass of a creeping animal lasts only until nightfall, so too, a mat rendered impure by a corpse remains impure only until nightfall.

In response to this, Rava said: This opinion does not lead to that conclusion, as there is a Torah edict indicating otherwise. The verse states (Numbers 31:24): “And you shall wash your garments on the seventh day.” This teaches that any ritually impure items that you render impure due to contact with a corpse must remain impure for a period of no less than seven days. Therefore, since it has been inferred that the mat is susceptible to the impurity imparted by a corpse, it automatically falls into the same category of other items similarly rendered impure by a corpse and must remain impure for a period of at least seven days.

§ Up to this point, the Gemara discussed how to properly apply the principle: It is sufficient for the conclusion that emerges from an a fortiori inference to be like its source. It now returns to discussing the main subject of the mishna, which is the various views concerning Goring, the primary category of damage. The Gemara suggests: And let one be held liable for Eating and Trampling if these take place in the public domain. This can be inferred via an a fortiori inference, as follows: And if with regard to damage classified as Goring, for which, if it took place on the property of the injured party, according to the Rabbis one is liable to pay only half the cost of the damage, yet the owner of the animal is nevertheless liable for damage caused in the public domain, then with regard to damage classified as Eating and Trampling, whose halakhot are more strict, as one pays the full cost of the damage caused on the property of the injured party, is it not right that one should be liable for damage caused in the public domain?

The Gemara rejects this: The verse states with regard to Eating or Trampling (Exodus 22:4): “And it consumed in the field of another,” meaning that one’s liability for this form of damage is limited to damage caused on the property of the injured party, but not for damage caused in the public domain.