Bava Kamma 80B

שמואל לא עייל קמיה דרב אסי, רב אסי לא עייל קמיה דרב. אמרי: מאן נתרח? נתרח שמואל וניתי רב ורב אסי.

Shmuel would not enter before Rav Asi, as he considered Rav Asi to be greater than he; and Rav Asi would not enter before Rav, as Rav was his teacher. They said: Which of us should stay behind and let the other two come in before him? They decided: Let Shmuel stay behind, and let Rav and Rav Asi come inside in that order. Afterward, Shmuel himself would enter.

ונתרח רב או רב אסי! רב ⁠– מילתא בעלמא הוא דעבד ליה לשמואל; משום ההוא מעשה דלטייה, אדבריה רב עליה.

The Talmud asks: And why didn’t they decide to let Rav or Rav Asi stay behind? The Talmud explains: It was a mere gesture that Rav performed for Shmuel in initially stating that Shmuel should precede him, as Rav did not really feel that Shmuel was superior to him. Rather, on account of that incident in which he inadvertently cursed Shmuel, Rav took upon himself to treat Shmuel with deference.

אדהכי והכי, אתא שונרא קטעיה לידא דינוקא. נפק רב ודרש: חתול ⁠– מותר להורגו, ואסור לקיימו, ואין בו משום גזל, ואין בו משום השב אבידה לבעלים.

In the meantime, while all this was going on, a cat [shunara] came and severed the hand of the baby. Rav emerged from the house and taught: With regard to a cat, it is permitted to kill it even if it is privately owned; and it is prohibited to maintain it in one’s possession; and it is not subject to the prohibition against theft if one takes it from its owner; and, in the case of a lost cat, it is not subject to the obligation of returning a lost item to its owner.

וכיון דאמרת ״מותר להורגו״, מאי ניהו תו ״אסור לקיימו״? מהו דתימא: מותר להורגו, איסורא ליכא; קא משמע לן.

The Talmud asks a question with regard to Rav’s statement: And since you said that it is permitted to kill it, what is the need to state further that it is prohibited to maintain it in one’s possession? If a cat is considered such a dangerous animal that it is permitted to kill it, of course one cannot keep it in his possession. The Talmud answers: Lest you say that although Rav ruled that it is permitted to kill it, he concedes that there is no prohibition in keeping it, Rav therefore teaches us that it is also prohibited to keep it in one’s possession.