גמ׳ אמר רבי אבא אמר רב חייא בר אשי אמר רב: נכנסה לו צפור תחת כנפיו — יושב ומשמרה עד שתחשך. מתיב רב נחמן בר יצחק: ישב הראשון על הפתח ומלאהו, ובא השני וישב בצדו, אף על פי שעמד הראשון והלך לו — הראשון חייב והשני פטור. מאי לאו, פטור אבל אסור? לא, פטור ומותר. הכי נמי מסתברא, מדקתני סיפא: למה זה דומה — לנועל את ביתו לשומרו ונמצא צבי שמור בתוכו, מכלל דפטור ומותר! שמע מינה.
Talmud: R' Abba said that Rav Ḥiyya bar Ashi said that Rav said: If a bird flew under the flaps of one’s clothing on Shabbat and cannot get out, he may sit and secure it until dark and then take it. Rav Naḥman bar Yitzḥak raised an objection based on that which we learned in the Mishnah: If the first person sat in the doorway and filled it, and a second person came and sat next to him, the first person is liable and the second is exempt, even if the first person stood and went. What, does this not mean here, as it does throughout tractate Shabbat, that he is exempt after the fact, but it is prohibited to do so ab initio? How then could Rav say one may sit and secure the bird ab initio? The Talmud rejects this: No, the statement in the Mishnah means that he is exempt and it is permitted ab initio. The Talmud adds: So too, it is reasonable to explain the Mishnah that way from the fact that it was taught in the latter clause of the Mishnah: To what is this second person’s action similar? To one who locks his house to secure it, and it turns out a deer that was trapped before Shabbat is also secured inside it. By inference, he is exempt and it is permitted, just like one who locks the door to his house. The Talmud concludes: Indeed, learn from it that it is so.