Bava Kamma 72A

דלא אכלי בשרא דתורא.

is because I had not eaten ox meat. In other words, I was fasting yesterday and was unable to concentrate properly.

ואלא מאי שנא רישא ומאי שנא סיפא?

Rava responded to him: But if the Torah requires even a partial payment of the fourfold or fivefold payment, what is different in the first clause, in which the son must pay, and what is different in the latter clause, where he is exempt?

אמר ליה: רישא קרינא ביה ״וטבחו״ כולו באיסורא, סיפא לא קרינא ביה ״וטבחו״ כולו באיסורא.

Rav Naḥman said to him: In the first clause, where the father’s animal was stolen and slaughtered in his lifetime, I read about this case the verse: “If a man steal an ox or a sheep, and slaughter it” (Exodus 21:37), which indicates that the thief slaughtered the ox or the sheep entirely in a prohibited manner. In the latter clause, where the animal was slaughtered after the father’s death, I do not read about this case the verse: “And slaughter it,” which describes a slaughter that was performed entirely in a prohibited manner, because the animal already partially belonged to him, and his own portion of the ox was slaughtered in a permitted manner.

השוחט ונמצאת טריפה וכו׳. אמר ליה רב חביבי מחוזנאה לרב אשי: שמע מינה, אינה לשחיטה אלא לבסוף.

§ The Mishnah teaches: A thief who slaughters the animal but it was found to be a tereifa, and likewise a thief who slaughters a non-sacred animal in the Temple courtyard, pays the fourfold or fivefold payment. Rav Ḥavivi of Meḥoza said to Rav Ashi: Conclude from the Mishnah that the act of slaughtering is considered to have been performed only at the end of the slaughtering process.

דאי ישנה לשחיטה מתחילה ועד סוף, כיון דשחט בה פורתא ⁠– אסרה, אידך ⁠– לא דמריה קא טבח!

Rav Ḥavivi of Meḥoza explains: As, if you say that the act of slaughtering lasts from beginning to end, i.e., the halakhic ramifications of slaughtering are in effect throughout the process, one could raise a question with regard to the case of one who slaughters a non-sacred animal in the Temple courtyard: Once he slaughtered the animal a bit, at the very start of the act of slaughter, he has prohibited the animal, with regard to deriving benefit, as a non-sacred animal slaughtered in the Temple courtyard. When he slaughters the other part, it is already prohibited with regard to deriving benefit, which means that it is not an animal that belongs to its owner that he slaughters. Since deriving benefit from the animal is prohibited, it has no value; therefore, there is no ownership.