Eruvin 70A

ליגזר דילמא אתי לבטולי להו. קא משמע לן.

Let us issue a decree that two residents may not give away their rights in a domain, lest people come to renounce their rights in favor of two residents as well. People might assume that just as two may give away their rights to one, so too may one give away his rights to two. The Mishnah therefore teaches us that we do not issue such a decree.

ואין נוטלין רשות. למה לי? לא צריכא, אף על גב דאמרי ליה: קני על מנת להקנות.

We learned in the Mishnah: But two may not receive rights in a domain. The Talmud poses a question: Why do I need to say this? Isn’t it superfluous? The Talmud answers: No, it is necessary to teach that rights may not be acquired even if the other residents of the courtyard say to one of the two who did not establish an eiruv: Acquire our rights in the courtyard on condition that you transfer them in turn to your friend, the other one who did not establish an eiruv. The Mishnah teaches that he does not become their agent and cannot transfer the rights to the other person, as he himself cannot receive such rights under these circumstances.

בעא מיניה אביי מרבה: חמשה ששרויין בחצר אחת, ושכח אחד מהן ולא עירב, כשהוא מבטל רשותו צריך לבטל לכל אחד ואחד או לא? אמר ליה: צריך לבטל לכל אחד ואחד.

Abaye raised a dilemma before Rabba: If 5 people live in the same courtyard, and one of them forgot to join in an eiruv, when he renounces his rights in the courtyard, must he renounce them in favor of each and every one of the others or not? Rabba said to him: He must renounce his rights in favor of each and every one.