Just as the redemption of your firstborn son does not apply to a child who was purchased or received as a gift, i.e., the mitzva applies only to one’s own son, so too, the mitzva of separating tithe from your flock and your herd does not apply to animals that were purchased or received as a gift.

The Gemara raises a difficulty: But this verse, which juxtaposes the firstborn son to an animal, is written with regard to redemption of a firstborn, not with regard to animal tithe. The Gemara explains that the verse states: “So you shall do with your oxen, and with your sheep: Seven days it shall be with its mother; on the eighth day you shall give it to Me” (Exodus 22:29). If this is not needed for the matter of firstborn animals, which do not require any action to sanctify them as the animal is already consecrated when it leaves the womb, apply it to the matter of animal tithe, where an animal is sanctified only when the owner counts it as the tenth animal.

The Gemara suggests: But instead one can say to apply this phrase: “So you shall do,” to the matter of a sin offering and a guilt offering rather than animal tithe, i.e., one should derive that these offerings are sanctified only if they originally belonged to the individual who is attempting to sanctify them, not if they are purchased or received as a gift. The Gemara explains that one expounds the phrase as referring to animal tithe because that case is similar to the case of: Your son. Just as your son does not come to be redeemed to atone for a sin, so too, the phrase: Your sheep and your oxen, discussed in the verse, is referring to animal tithe, which does not come to the Temple to atone for a sin. Sin offerings and guilt offerings are brought only if one commits a sin.

The Gemara suggests: But instead one can say to apply this phrase to the matter of a burnt offering and a peace offering, which can be brought even if one has not sinned, like the animal tithe. The Gemara explains that one expounds the phrase as referring to animal tithe because that case is similar to the case of: Your son. Just as your son cannot come in the form of a vow or a gift, so too, the phrase: Your sheep and your oxen, discussed in the verse, is referring to animal tithe, which cannot be brought as a vow or as a gift. It is not referring to a burnt offering or a peace offering, both of which can be brought as a vow or as a gift.

The Gemara suggests: But one can say instead that one should apply this phrase to the matter of a burnt offering of appearance, which one brings when he ascends to Jerusalem on one of the three pilgrimage Festivals. This offering is not brought for a sin, nor as a vow or a gift, as it is obligatory. The Gemara explains that one expounds the phrase as referring to animal tithe because that case is similar to the case of: Your son. Just as your son does not have a fixed time of year to be redeemed, but is redeemed after the thirtieth day from his birth, so too: Your oxen and your sheep, discussed in the verse, is referring to animal tithe, which does not have a fixed time to be brought. By contrast, the burnt offering of appearance is brought only on the three pilgrimage Festivals.

The Gemara asks: If the halakha of the tithing of a purchased animal is derived from the juxtaposition to the mitzva of redemption of a firstborn son, then all the halakhot of one should apply to the other: Just as your firstborn son cannot be purchased at all, under any circumstances, so too, your oxen and your sheep should not be subject to animal tithe if they are purchased at all. If so, why does Rabbi Asi say that Rabbi Yoḥanan says: If one purchased ten animal fetuses while they were still in their mothers’ wombs and the animals were born once he already owned them, they all enter the pen to be tithed? If the halakha is derived from a firstborn son, there should be no concept of tithe in the case of purchased animals.

Rava said in response that the verse states: “So you shall do with your oxen, and with your sheep: Seven days it shall be with its mother; on the eighth day you shall give it to Me.” The verse excludes purchased animals from animal tithe only at the time of doing, i.e., from the time the animals are fit to be sacrificed in the Temple, not while they are still in their mothers’ wombs, as at that time they are as yet unfit to be sacrificed on the altar.

The Gemara discusses the matter itself, to cite the relevant discussion in full. Rabbi Asi says that Rabbi Yoḥanan says: If one purchased ten animal fetuses while they were still in their mothers’ wombs and the animals were born once he already owned them, they all enter the pen to be tithed. The Gemara asks: But didn’t we learn in the mishna: One who purchases an animal or has an animal that was given to him as a gift is exempt from animal tithe? If so, why isn’t the owner of these fetuses also exempt from animal tithe?

Rabbi Elazar said: I saw Rabbi Yoḥanan in a dream, which is a sign that I am saying a proper matter in explaining his opinion. The verse states: “So you shall do” (Exodus 22:29); the verse excludes purchased animals from animal tithe only at the time of doing, i.e., from the time the animals are fit to be sacrificed in the Temple. Rabbi Shimon ben Elyakim raised an objection to Rabbi Elazar from a baraita: The exemption of a purchased animal applies even to an animal whose time has not yet arrived, i.e., before it is eight days old and fit to be sacrificed in the Temple. By the same token, the exemption should also apply to a fetus, despite the fact that it is not yet fit to be sacrificed.

Rabbi Elazar said to Rabbi Shimon ben Elyakim: This baraita is not a tannaitic source that can be relied upon, as it is not accurate. And if you say this baraita is a tannaitic source that can be relied upon, it is only in accordance with the opinion of Rabbi Shimon ben Yehuda in the name of Rabbi Shimon, who says that an animal whose time has not yet arrived also enters the pen to be tithed, and in this regard it is like a firstborn animal. Just as a firstborn animal is sanctified before its time arrives to be sacrificed, but is sacrificed after its time, i.e., after it is at least eight days old, so too, an animal whose time has not yet arrived enters the pen to be tithed, and if it comes out as the tenth animal, it is sanctified before its time for sacrifice has arrived but is sacrificed only after its time, i.e., after it is at least eight days old.

A tanna taught a baraita in the presence of Rav: Which is the type of animal set aside as payment to a prostitute, about which the Sages said (see 57a) that it enters the pen to be tithed? Any animal that he gave to her as payment and subsequently purchased back from her. The tanna asked: But doesn’t it become disqualified from the status of animal tithe as a purchased animal, as he purchased it back from the prostitute?

The Gemara answers that this statement escaped that tanna: As Rabbi Asi says that Rabbi Yoḥanan says: If one purchased ten animal fetuses while they were still in their mothers’ wombs they all enter the pen to be tithed. Accordingly, the baraita can be understood as referring to an animal that was given to a prostitute as payment and purchased back from her while it was still inside its mother’s womb.