Bava Kamma 68B

תדע שסתם גניבה יאוש בעלים הוא –

Know that an ordinary case of theft is assumed to result in the owner’s despair of recovering the stolen item. In other words, in the absence of evidence to the contrary, one may assume that the victim of theft has despaired of recovering his item.

שהרי אמרה תורה: טבח ומכר ⁠– משלם תשלומי ארבעה וחמשה. ודלמא לא אייאש! אלא לאו משום דאמרינן: סתם גניבה ⁠– יאוש בעלים היא.

The reason is that the Torah stated that if a thief slaughtered or sold the animal he had stolen, he pays the fourfold or fivefold payment. But why is this so? Perhaps the owner did not yet despair at the time the thief sold the animal, in which case the sale is invalid, and there should be no fourfold or fivefold payment. Rather, is it not because we say that an ordinary case of theft is assumed to result in the owner’s despair of recovering the stolen item? This concludes the statement of R' Elazar, which clearly indicates that there is no fourfold or fivefold payment if the animal is sold before the owner’s despair.

ודלמא אף על גב דלא אייאש!

The Talmud asks a question with regard to R' Elazar’s assumption: But perhaps the Torah obligates the thief to pay the fourfold or fivefold payment even if the owner has not yet despaired at the time of the sale, despite the fact that the sale is invalid, as Rav Naḥman stated.

אמרי: לא סלקא דעתך; דומיא דטביחה ⁠– מה טביחה דאהנו מעשיו, אף מכירה דאהנו מעשיו. ואי לפני יאוש, מאי אהנו?

In response to this question the rabbis say: This cannot enter your mind, as R' Elazar maintains that the juxtaposition of slaughtering and selling in the verse that states: “And slaughter it or sell it,” teaches that the thief’s sale of the animal is similar to his slaughter of it. Just as slaughter is a matter in which his action was effective, so too, the case of selling the animal is one in which his action was effective, i.e., the sale is valid. And if the sale occurred before the owner’s despair, in what sense were his actions effective?