Yevamot 27A

חלץ לאחיות ⁠— לא נפטרו צרות. היכא דקיימא חליצה דשמעון חליצה כשרה, חליץ לה ראובן חליצה פסולה?

In the case of 3 brothers, two of whom were married to several women, including two sisters, and the two married brothers later died, and their wives happened before the yavam for levirate marriage, if the yavam performed ḥalitza with the sisters who were among the wives, the rival wives are not thereby exempt. One can deduce from here that since the yavam cannot consummate the levirate marriage with the sisters, as each is the sister of a woman with whom he has a levirate bond, then the act of ḥalitza is invalid, and invalid ḥalitza is ineffective in exempting their rival wives. It is concluded from here that even Shmuel requires valid ḥalitza, i.e., ḥalitza that occurs when there is a possibility of consummating the levirate marriage. According to this rationale, however, Shmuel’s ruling in the above case is difficult: With regard to the second sister, when there exists the possibility for Shimon’s ḥalitza, i.e., the ḥalitza of the second brother who did not yet perform ḥalitza, to be a valid ḥalitza, would it be allowed for Reuven, the brother who already did ḥalitza with one sister, to perform invalid ḥalitza with her?

מאי ״אחד חולץ לכולן״ נמי דקאמר ⁠— אאמצעית. והא ״כולן״ קאמר! כיון דרובה גביה, קרי ליה ״כולן״. ואיבעית אימא: כי קאמר שמואל חליצה מעליא בעינן ⁠— הני מילי למיפטר צרתה, אבל מפטרא נפשה ⁠— פטרה.

The Talmud resolves this difficulty by reinterpreting Shmuel’s statement. What does it mean that it says: One performs ḥalitza with each of them, that Shmuel stated? Shmuel says that with regard to the middle one, i.e., the third sister, one of the two brothers performs ḥalitza with her. The Talmud asks: But didn’t he say: Each of them, indicating that one brother performs ḥalitza with all of the sisters? The Talmud answers: Since the brother who performed ḥalitza with one sister repeats the act with another, it turns out that most of the acts of ḥalitza are performed with him, and this is called: With each of them. And if you wish, say a different answer: When Shmuel said we require a full-fledged ḥalitza, this applies only to exempt her rival wife by means of that ḥalitza. But to exempt the woman herself, even invalid ḥalitza would render her exempt. In the case above, since no rival wives are involved, it would be sufficient for one brother to perform ḥalitza with each of the sisters.