The discussion begins with a ruling from Rabbi Ila'a: If someone steals a lamb (taleh) and it grows into a ram (ayil), or a calf (egel) and it grows into an ox (shor), a change (shinui) has occurred while the item was in the thief's possession, and the thief acquires it (koneh). What does it mean that the thief acquires it? Rashi clarifies that this acquisition is for a specific purpose: if the thief slaughters or sells the animal after this change, he is exempt from paying the fourfold or fivefold penalty (arba'ah v'chamisha) that typically applies to a thief who slaughters or sells a stolen animal. This is because, at that point, the animal is considered his own. However, the thief is still obligated to pay the principal (keren) and double (kefel) value. The principal is paid according to the animal's current value, and the double payment is either based on its value at the time of the theft or at the time of judgment, depending on the specific case.
To elaborate on Rashi's interpretation, if a stolen item undergoes a change in the thief's possession, it becomes the thief's absolute property. Consequently, the thief must pay the original owner the item's value at the time of the theft, rather than returning the item itself. Rabbi Ila'a introduces the novel concept that even a natural progression, like an animal growing from a lamb to a ram, constitutes a significant change. This acquisition by the thief can be either stringent or lenient. If the item depreciates after the change, the thief cannot return the item itself but must pay its full value at the time of the theft. Conversely, if the item appreciates, the thief only pays its value at the time of the theft and benefits from the appreciation, as the change makes the item his.
However, Rashi's explanation presents a challenge. He states that the thief acquires the animal "for the purpose of slaughtering and selling" (le'inyan tevicha u'mechira), meaning "I slaughter what is mine, and I sell what is mine," thereby exempting him from the fourfold or fivefold penalty. Yet, Rashi also implies that this change is not a complete acquisition (kinyan gamur). If the item remains intact, the thief must return it to the owner. This raises a question: how can the thief acquire the item for the purpose of slaughtering or selling it, yet not own it completely if it remains intact? Many early commentators (rishonim), including Tosafot, disagree with Rashi, arguing that such a change constitutes a complete acquisition, meaning the thief owns the item entirely and only needs to pay its value at the time of the theft, even if the item is still present.
Regarding the principal payment, Rashi states that it is paid according to the animal's current value. This differs from the general rule taught by Rav, who holds that the principal is paid according to the value at the time of the theft. Rashi's view here aligns with cases where an item is destroyed or consumed, which are considered a "new theft" (gezeilah) at the time of destruction or consumption. Thus, when the thief slaughters or sells the animal, it's as if he is destroying the owner's property at that moment, necessitating payment based on the current value. The double payment, Rashi notes, is either based on the value at the time of the theft or at the time of judgment, depending on further discussion in the Gemara.
The Gemara then presents a challenge to Rabbi Ila'a from Rabbi Chanina, citing a teaching (braita): If one steals a lamb and it becomes a ram, or a calf and it becomes an ox, the thief pays the double and fourfold or fivefold penalties "as it was when he stole it" (ke'ein sheganav), meaning according to the value at the time of the theft. This contradicts Rabbi Ila'a's position, as the thief is still liable for the fourfold or fivefold payment, implying that the change did not grant him ownership. Rabbi Ila'a responds by asking: If a natural change does not constitute acquisition, why would the thief pay according to the value at the time of the theft? He should pay according to the current value, as the act of slaughtering or selling would be a new theft of the transformed item.
Rabbi Chanina clarifies his position: He agrees that the thief does not pay according to the current value, but for a different reason. The thief can argue, "Did I steal an ox from you? Did I steal a ram from you?" Since the item has changed, even if the change doesn't grant ownership, the thief is not liable for the current, higher value of the transformed animal. He is still liable for the fourfold or fivefold payment because the item fundamentally belongs to the original owner, but the payment is based on the original value. Rabbi Ila'a rejects this reasoning, exclaiming, "May God save us from such a view!" Rabbi Chanina retorts, "On the contrary, may God save us from your view!" This exchange highlights a fundamental disagreement: Rabbi Ila'a believes natural change grants the thief acquisition, while Rabbi Chanina believes it does not, but the thief is still not fully liable for the item's appreciated value due to the change in its form.
Rabbi Zera then challenges Rabbi Chanina: Why doesn't a change in name (shinui hashem) constitute acquisition? Even if a physical change (shivcha degufa) isn't considered an acquisition in this context, the fact that the animal is now called by a different name (e.g., from lamb to ram, calf to ox) should be sufficient. Rava, citing Rav Assi, responds that a newborn ox is already called an ox, and a newborn ram is already called a ram, as evidenced by scriptural verses. Therefore, the change from a calf to an ox or a lamb to a ram is not considered a true change in name, and thus, it does not constitute an acquisition based on a change in name.
The Gemara then asks, even if Rabbi Ila'a's reasoning is sound, he still faces the challenge from the braita presented by Rabbi Chanina. Rav Sheshet resolves this by stating that the braita follows the opinion of Beit Shammai, who hold that a change does not grant acquisition (shinui lo koneh) and the item remains in its original status (bimkomo omedes). Beit Shammai's view is derived from the verse regarding the payment of a harlot (etnan zona), where the word "also" (gam) is interpreted to include even changed items in the prohibition against bringing them as offerings. Beit Hillel, on the other hand, interprets a different word to exclude changed items, implying that a change does grant acquisition. Therefore, Rabbi Ila'a, who holds that a natural change grants acquisition, can simply say he follows Beit Hillel, not Beit Shammai.
The Gemara then states that up to this point, the dispute between Rabbi Ila'a and Rabbi Chanina centered on whether a natural change grants acquisition. However, regarding the payment itself, everyone agrees that it is based on the value at the time of the theft. This leads to a challenge against Rav, who taught that the double and fourfold or fivefold payments are based on the value at the time of judgment. Rava resolves this by distinguishing between paying in kind (e.g., returning animals) and paying in money. If one pays in kind, the payment is based on the value at the time of the theft, as "he stole a lamb and pays a lamb." If one pays in money, the payment is based on the current value. Thus, the braita refers to paying in kind, while Rav's ruling refers to paying in money.
Rabbah then states that a change (shinui) grants acquisition. This refers to a physical change made by the thief (shinui b'yadayim), such as transforming wool into a garment. In such a case, the thief does not return the original object but pays its monetary value. This principle is derived from a biblical verse, "And he shall return the stolen item that he stole" (V'heshiv et hagezeila asher gazal), implying that only if it's "as it was when he stole it" must the actual item be returned; otherwise, money is paid. A Mishnah also supports this: if one steals wood and makes it into vessels, or wool and makes it into garments, he pays according to the value at the time of the theft. Another proof comes from the law of "first shearings" (reishit hagez) given to the priest (Kohen): if the owner dyes the wool before giving it, he is exempt, because the change grants him acquisition, and he doesn't even pay money, as the priest cannot compel him to give it to any specific priest.
The Gemara then turns to the concept of despair (yiush), where the owner gives up hope of recovering the stolen item. The Sages (Rabbanan) decreed that despair grants acquisition to the thief. The question arises whether this acquisition is by Torah law (de'oraita) or Rabbinic enactment (derabbanan). One side argues it's by Torah law, comparing it to finding a lost object (motzei aveidah): if the owner despairs before the finder acquires the object, the finder keeps it. Similarly, a thief might acquire a stolen item through despair. The other side argues that a lost object comes into the finder's possession permissibly, while a stolen item comes into the thief's possession illicitly. Therefore, despair might only grant acquisition by Rabbinic enactment, specifically for the "repentant" (takanat hashavim), to encourage thieves to repent by allowing them to pay money instead of returning the transformed item.
Rav Yosef, however, asserts that despair does not grant acquisition, not even by Rabbinic enactment. This means that a thief must always return the actual item, regardless of the owner's despair. This sets up a debate between Rabbah (who holds despair grants acquisition) and Rav Yosef (who holds it does not).
Rav Yosef challenges Rabbah: If one stole leavened bread (chametz) and Passover passed, the thief can tell the owner, "Here is yours before you." This implies the thief does not have to pay money, even though the chametz is now worthless. But since the owner surely despaired before Passover, and Rabbah holds despair grants acquisition, the thief should have acquired the chametz and be obligated to pay its original value. Rabbah responds that despair grants acquisition only when the owner despairs, and the thief intends to acquire the item. In the case of chametz, the thief also does not want to acquire it on Passover, as it is forbidden to possess. Therefore, despair does not grant acquisition in this specific case, and the thief can return the worthless item.
Abaye then challenges Rabbah regarding the law of offerings (korbanot): "His offering, and not a stolen one." This implies that a stolen animal cannot be brought as an offering. Abaye argues that this must refer to a case where the owner despaired, and yet the animal cannot be offered, proving that despair does not grant acquisition. Rabbah refutes this, explaining that the verse refers either to an animal stolen before the owner despaired (in which case it's obviously not the thief's to offer) or, more likely, to an animal already consecrated as an offering. In the latter case, the prohibition against offering a stolen item means that even if the thief intended to offer it for the original owner, it's invalid, or that one cannot steal a consecrated item at all, as it belongs to God. Thus, this verse does not prove that despair does not grant acquisition.
Finally, Abaye challenges Rav Yosef (who holds despair does not grant acquisition) from a Mishnah concerning animal hides. The Mishnah states that a private owner's (ba'al habayit) intention (machshava) can make hides susceptible to ritual impurity (tumah), but a tanner's intention cannot. Crucially, it states that a thief's intention can make hides susceptible to tumah, while a robber's (gazlan) intention cannot. The explanation is that a thief operates secretly, so the owner despairs, and the thief acquires the hides, making his intention effective. A robber operates openly, so the owner does not despair. This Mishnah implies that despair grants acquisition, contradicting Rav Yosef. (Rabbi Shimon reverses the cases of thief and robber, but the underlying principle remains that despair grants acquisition.)
Rav Yosef initially responds that the Mishnah refers to a case where the thief cut the hides (shekatzetzan), which constitutes a physical change (shinui ma'aseh) and grants acquisition, not merely despair. However, Rav Papa bar Rav Chanan objects, noting that the Mishnah refers to hides used for a "finger-mat" (etzba), a type of table mat that does not require cutting for its functionality; any cutting is merely decorative. Therefore, the intention alone would make it susceptible to tumah, and despair would still be the underlying factor for acquisition. This question troubled Rabbah for 22 years, until Rav Yosef, upon becoming the head of the academy, provided an answer: a change in name (shinui hashem) is equivalent to a physical change (shinui ma'aseh). When the thief takes a hide (mashka) and intends to make it a tablecloth (abarzin), the change in name itself grants acquisition, regardless of whether despair occurred. Thus, the Mishnah does not prove that despair alone grants acquisition.
The Gemara then challenges this new concept of "change in name" from the case of a stolen crossbeam (marish) built into a building. Although the beam's name changes from "beam" to "roof," the Mishnah states that the thief must pay money only "due to the enactment for the repentant" (mipnei takkanat hashavim), implying that without this enactment, he would have to return the actual beam. This suggests that a change in name does not grant acquisition. Rav Yosef responds that a beam remains a "beam" even when part of a roof, as evidenced by a prophetic verse, so there is no actual change in name in this case. Thus, Rav Yosef successfully defends his position that despair alone does not grant acquisition.