QUESTION: The Gemara (66b) discusses a case in which the outer Chatzer and inner Chatzer made an Eruv together. They placed the actual Eruv in the inner Chatzer. However, one of the residents of the inner Chatzer forgot to join the Eruv. The Gemara says that the people in the inner Chatzer may not carry, because the resident of the inner Chatzer who forgot to join the Eruv cannot be Mevatel his Reshus to the residents of the outer Chatzer.

Rav Huna brei d'Rav Yehoshua asks that the person who forgot should simply be Mevatel his Reshus to the residents of the inner Chatzer who made the Eruv. He does not need to be Mevatel his Reshus to each person who joined the Eruv, and thus he does not need to be Mevatel his Reshus to the residents of the outer Chatzer. The Gemara concludes that he does need to be Mevatel his Reshus to all of the people who made the Eruv. In this case, since he cannot be Mevatel his Reshus to the outer Chatzer (because Bitul from one Chatzer to another Chatzer is not permitted), he cannot be Mevatel his Reshus at all.

Why does Rav Huna brei d'Rav Yehoshua ask this question only in this case? The Gemara describes another case which is the exact complement of the case that Rav Huna brei d'Rav Yehoshua discusses. The Gemara says that if an Eruv was made in the outer Chatzer and one of the residents of the outer Chatzer forgot to participate, the residents of both Chatzeros are forbidden to carry. Rav Huna brei d'Rav Yehoshua should have asked that in that case as well the person in the outer Chatzer should be Mevatel Reshus to the other residents of the outer Chatzer if he does not need to be Mevatel to every person who made the Eruv (including those in the inner Chatzer). Why does he not ask that question?

(a) The RITVA answers that Rav Huna brei d'Rav Yehoshua indeed could have asked his question in that case as well.

(b) TOSFOS (DH k'Man) answers that in the case of the Eruv in the outer Chatzer in which a resident of the outer Chatzer forgot to join, in order to permit carrying in the outer Chatzer the Bitul Reshus must be done to the residents of the inner Chatzer as well. Since the residents of the inner Chatzer normally walk through the outer Chatzer, and they are prohibited to carry in their own Chatzer without a valid Eruv, they prohibit the outer Chatzer from carrying as well (because of "Regel ha'Asurah bi'Mekomah"). In such a case, the person who needs to be Mevatel his Reshus must relate directly to the members of the inner Chatzer. It does not suffice to be Mevatel his Reshus only to the people in the outer Chatzer so that the people in the inner Chatzer are automatically joined with them, because doing so is also considered being Mevatel Reshus from one Chatzer to another ("Bitul Reshus me'Chatzer l'Chatzer").

Rav Huna brei d'Rav Yehoshua asks his question only in the first case, in which the Eruv is located in the inner Chatzer and one of the residents there forgot to join the Eruv. In that case, the people in the outer Chatzer are not considered residents of the inner Chatzer, because they do not normally walk through the inner Chatzer. Rather, they are considered to be members of the inner Chatzer only because of "Hergel Eruv" (see Insights to Eruvin 66:2b). Therefore, Rav Huna brei d'Rav Yehoshua assumes that it suffices for a person to be Mevatel his Reshus to the residents of the inner Chatzer, and he should not have to relate directly to the residents of the outer Chatzer. Once he is Mevatel to a neighbor from the inner Chatzer, the members of the inner Chatzer automatically join with those of the outer Chatzer through the Eruv that they all made together.