(Beraisa - R. Eliezer): If [the key] was lost in the field, it is not an Eruv. If it was lost in the city, it is an Eruv.

If it was lost in the field, it is not an Eruv, for he cannot bring it [to his place] via a path [that requires only an Isur mid'Rabanan, i.e.] Shevus (PNEI MEIR). If it was lost in the city, it is an Eruv, for he can bring it via a path [for which one who carries on it is] exempt.

Question: R. Eliezer said properly! What is Rabanan's reason?

Answer #1 (R. Ba brei d'Rav Papi): They hold like R. Meir. R. Meir says that one may open [a house of arranged bricks that were not cemented] and take [food that is inside. It is not Muktzah.]

Objection: R. Meir said so about Yom Tov. Did he say so about Shabbos? Here we discuss Shabbos!

Answer #2 (Rav Avmari): They hold like R. Eliezer ben Yakov;

(Mishnah - R. Eliezer ben Yakov): We may tie in front of an animal lest it leave;

Tying and locking are the same. (Even regarding land, it is not Binyan, so one may break the lock even on Shabbos - SEFER NIR.)

Limitation: [The Tana'im argue about] a stone cabinet, but a wood cabinet, [all agree that it is an Eruv, for] this is like breaking a barrel to eat dried figs from it.

(Mishnah): If the Eruv rolled outside the Techum, or a pile of rocks fell on it [so now it is buried], or it was burned, or it was Terumah and it became Tamei - if this was before Shabbos, the Eruv is invalid. If it happened on Shabbos, it is valid.

If we are in Safek [whether it was before or on Shabbos], R. Meir and R. Yehudah say, he is in Chamar Gamal (like one prodding a donkey from the back and leading a camel from the front, i.e. he is constrained in two directions.)

R. Yosi and R. Shimon say, a Safek Eruv is valid.

R. Yosi: Avtulus testified in the name of five Chachamim that a Safek Eruv is valid.

(Gemara): [R. Yosi and R. Shimon] said [that a Safek Eruv is valid] only if it became Tamei, and it is a Safek whether it became during the day (Erev Shabbos) or after dark, but if it was Safek Tahor, Safek Tamei [when he placed the Eruv, all agree that] one may not be Me'arev with it.

(R. Shmuel bar Nachman citing R. Yonason): They follow Chazakos. (If it was initially Tahor, the Chazakah is that it was still Tahor Bein ha'Shemashos. If it was initially Safek, the Chazakah was that he has the Techum of his city. It is a Safek whether or not that changed, so we follow the Chazakah, and says that it did not change.)

Question (R. Meir and R. Yehudah, to R. Yosi and R. Shimon): If it was consumed during the day, is he not forbidden [to rely on it to leave the Techum]?!

Answer (R. Yosi and R. Shimon): He has his Heter (before we learned of the Safek, the Chazakah was that the Eruv is Kosher), until you know that he is forbidden.

Question (R. Yosi and R. Shimon, to R. Meir and R. Yehudah): If it was consumed after dark, is he not permitted?!

Answer (R. Meir and R. Yehudah): He is forbidden, until you know that he is permitted.

Question: [According to R. Meir and R. Yehudah,] do we give to him 2000 Amos from his Eruv to his house? (Perhaps he uprooted his intent from the Techum of his city, and he did not get the Techum of his Eruv, due to Safek. We explained this like PNEI MEIR.)

Answer #1 (R. Ba bar Mamal): We give to him.

Answer #2 (R. Shmuel bar Rav Yitzchak): We do not give to him.

(R. Shamai, in front of R. Yosah, in the name of R. Acha): [R. Ba and R. Shmuel] argue according to R. Meir, but according to R. Yehudah, all agree that we give to him.

[According to R. Shmuel bar Rav Yitzchak,] Chamar Gamal of R. Meir is unlike Chamar Gamal of R. Yehudah. Chamar Gamal of R. Meir, he does not [have the Techum of] his Eruv, for his Eruv did not acquire for him. He is not like people of his city, since he intended to uproot himself from the Techum of his city;

Chamar Gamal of R. Yehudah [allows him between his house and his Eruv], since he did not intend to uproot himself from the Techum of his city.