Explanation #1 (Rashi): He challenged him from a Mishnah about Yom Tov and Shabbos, because no other Mishnah explicitly discusses taking an Eruv.

Rebuttal (and Explanation #2 - Ri): He challenged him specifically from Yom Tov. However, this that [the Mishnah] requires taking the Eruv for one who comes to be Me'arev on Erev Shabbos, he could not ask, for Bein ha'Shemashos, which is when Eruv acquires, he cannot bring it there, due to the Isur of Hotza'ah.

Suggestion: We can resolve Rashi. Surely he could have challenged him from Eruv of the entire year (a regular Shabbos). Why must he bring it to the desired place of Shevisah?

He needs only to take it out of his house and leave it in Reshus ha'Rabim in a nearby place, [within] two thirds of a Mil, or three quarters of a Mil, or half a Mil [of the place of his desired Shevisah], which are the distances one can walk during Bein ha'Shemashos, according to the three opinions (of the duration of Bein ha'Shemashos), for if he wants, he can bring it less than four Amos at a time until the place of his Shevisah!

Rejection - part 1: According to Rabanan of Rebbi, he could not bring it less than four Amos at a time. Therefore, he must take it to the place of his Shevisah;

Rejection #1 - part 2: Also according to Rebbi, we can say that he needs to take it to the place of his Shevisah, i.e. when he was Shoves in Reshus ha'Yachid, and there is Reshus ha'Rabim between his house and the place of his Shevisah.

Comment: However, when his Shevisah was in Reshus ha'Rabim, he need not bring it to the place of his Shevisah. You are forced to say that this is the truth according to Rashi;

If he must always bring it to the place of his Shevisah, if so [Rav bar Sheva] should ask from Rebbi, and [R. Zeira] could not answer what he answered, that we decree due to Shabbos after Yom Tov. Until here is the comment.

Rejection #2 - part 2 (Ri): Even when his Shevisah was in Reshus ha'Rabim, he must bring it to the place of his Shevisah also according to Rebbi, for Rebbi agrees that we should be stringent about the Shevus of less than four Amos at a time, just like he agrees about a reed;

He decrees lest one break it, for easily one can come to a Torah Isur of Shabbos. Likewise, we should be stringent about this Shevus (less than four Amos at a time).

Implied question: When we answer that it is a decree due to Yom Tov after Shabbos, we could have answered that it is a decree due to every Shabbos. In several places we say that we decree due to Shabbos!

Answer #1: It is better to decree Yom Tov due to Yom Tov.

Answer #2: Even though normally we decree, regarding Eruv, for which we are more lenient, we do not decree Yom Tov due to Shabbos.

Implied question: Above (32b), it says about [using] a tree that anything due to Shevus, [Chachamim] did not decree about it Bein ha'Shemashos, and we do not decree due to Yom Tov that falls after Shabbos or before Shabbos. Then, no matter what you will say (whether it is still day, or if it is already night) one may not use the tree!

Answer: This is because there, this itself (using a tree) is only due to Shevus, and it is forbidden to take it only mid'Rabanan;

However, here that Yom Tov falls after Shabbos, one cannot bring it due to the Isur Hotza'ah mid'Oraisa. We decree other Yomim Tovim due to this (Yom Tov after Shabbos).

Explanation #1 (Rashi, first Perush): He cannot take it from Karmelis and bring it to the top of the tower in which he was Shoves, for he takes it through air of Reshus ha'Rabim to Reshus ha'Yachid.

Question: Why is it not an Eruv? There is no Isur Torah, and [our Mishnah] is like Rebbi!

Source: [It is like Rebbi,] for it asks afterwards "if there is a window and a rope, indeed [it is an Eruv]!", and even though also when it is Agud in his hand, there is an Isur mid'Rabanan!

Explanation #2: It is not Karmelis, rather, Reshus ha'Rabim, e.g. it is in the ninth Tefach and many adjust loads on it, or it is a hole of Reshus ha'Rabim, which is like Reshus ha'Rabim.

Note: "The ninth Tefach" connotes that it is more than eight Tefachim, and at most nine. However, in Shabbos (8a), we say that if it is from three until nine, people do not step on it, and do not adjust on it. Presumably, "until nine" means until nine full Tefachim, just like "from three" refers to three full Tefachim! Most Meforshim say that the law applies from nine until 10. Perhaps Tosfos means "at the end of the ninth Tefach."

Question: This requires investigation, even if it is Reshus ha'Rabim, if in such a case this is Moshit (extending, to be liable mid'Oraisa), since he is not Moshit via land of Reshus ha'Rabim;

Note: Above, the Bach changed the text to say "a hole of Reshus ha'Yachid, which is like Reshus ha'Yachid. Kehilas Yakov says that according, here the text should say "even if it is Reshus ha'Yachid."

If it is not Moshit, we must say that we discuss when it is possible to extend from the top of the tower only through the window opposite the Eruv. He must bring it into the tower, and from there to the place of his Shevisah.

Explanation #1 (Ri): The Gemara holds that also when he tilts the top of the tower, his Shevisah is at the top of the tower, as long as the lower end does not leave its place;

If when the end of the tower was dislocated, his Shevisah is always in the place where the top was at the beginning when it was erect, i.e. in line with the bottom end, what was the answer "here we discuss a tall tower. If he tilts it, it goes outside four Amos"?

Why do we care if the top end went outside four Amos, since his Shevisah is not there?! Rather, surely his Shevisah is always at the top of the tower;

This is why he cannot tilt a long tower, for if he tilts it, it leaves the four Amos, and [his Shevisah] is four Amos from his Eruv, and he cannot bring his Eruv to the top of the tower.

This is even according to Rebbi, like I explained above (DH Amai), that he agrees that the Shevus of [carrying] less than four Amos at a time is forbidden [Bein ha'Shemashos].

Explanation #2 (Rashi): It is not an Eruv (when the tower is tall) because his Shevisah is distanced four Amos from its initial four Amos;

This is not its place, [Maharam - unless we would consider] it is as if he moved the entire tower from its first place and stood it up outside four Amos. Now, his Shevisah would be at the bottom of the tower, [like] at the beginning. Surely, we do not say "since if he would take it" so much [to be Machshir].

Implied question: Why didn't we ask this also above (32b) regarding a tree?

Answer #1: It is not normal to have a rope in a tree.

Implied question: He could bring a rope!

Answer: We do not say "Ho'il" so much.

Answer #2: We ask only here, since we said "he can tilt it."

Implied question: He could have said that it is [a valid Eruv] because one who places an Eruv has four Amos (32b. It is considered Reshus ha'Yachid!)

Answer: He wants to answer even if he intended his Shevisah to be outside of four Amos from the pit, similar to the Reisha [regarding a tree. We established that he was Shoves four Amos from his Eruv].

Implied question: Above (32b), regarding a tree, why didn't we answer that he intended his Shevisah to be outside of four Amos [from the tree? Rather, Rav Yitzchak answered that the tree leans four Amos from its trunk!]

Answer: It is normal to be Shoves at the trunk of the tree.

Explanation #1 (Rashi): This is a species of willow.

Objection: When it hardens, it becomes like full wood! The previous Beraisa should have listed it, and distinguished between Uzradin (when it became hard like a tree) and not Uzradin, like it distinguishes regarding reeds!

Explanation #2: It seems that it is a species of vegetable.

Question: Now we are thinking that we discuss a wooden tower, which is a Kli, since we answer "we discuss a tower of bricks." Also, a Stam tower in the Gemara is of wood;

If so, what was the question? He can break the Kli and take what is inside, like a Mishnah (Shabbos 146a) "one may break a barrel to take from it dried figs"! The reason is because Binyan and Stirah do not apply to Kelim.

Answer #1: It connotes to [the Makshan] that it is a big tower, to which Binyan and Stirah apply. If it were small, which is a Kli, why does R. Eliezer argue?

Answer #2: Binyan and Stirah apply also to a Kli, like it says in Shabbos (102a) "one who drives a peg into the handle of a hoe (so the blade will not fall off) is liable for building."

Implied question: It says below (35a) "he holds that it is a Kli, and Binyan [and Stirah] do not apply to Kelim"!

Answer #1: That refers to [Kelim] about which we say "one may take [a door from them], but one may not return." It is not absolute Binyan and Stirah.

Answer #2: It is like we establish in the conclusion, it is locked through ropes. Since we establish that it is locked through ropes, this connotes that it is permitted only like this, but not to break the Kli and ruin it, for Binyan and Stirah properly apply to Kelim.

Implied question: Why do we permit (Shabbos 146a) to break the barrel [to take the figs]?

Answer: In Beitzah (33b), we establish this to discuss Mustaki, i.e. pieces stuck together.

Implied question: According to R. Eliezer, who says that if he broke [fragrant wood] to smell it, he is exempt, but it is forbidden, we established it to discuss Mustaki! We asked "does R. Eliezer not hold that one may break a barrel...?"

Answer: Also Rabanan must establish it like this, for they agree that if one were Chayav Chatas [when he breaks off a chip] in order to clean his teeth, it would be forbidden to break in order to smell. (Since one can be Chayav Chatas for Binyan of Kelim, like Tosfos brought from Shabbos 102a, also they would forbid breaking a proper barrel.)

Implied question: Why did they ask Rav Sheshes (Shabbos 146a) whether one may pierce [the side of] a barrel with a spear [on Shabbos? Surely it is forbidden!]

Answer: [They asked] about Mustaki.

Remark: However, the Yerushalmi says about our Mishnah here "this refers to a stone tower. [One may break] a wooden tower. It is like breaking a barrel to take figs from it!"

Inference: Even if it is not Mustaki, it is permitted for a wooden Kli.

Explanation (Rashi): It is not forbidden due to Muktzah, for our Stam Mishnah is like R. Shimon (who permits Muktzah).

Question: It says in Beitzah (2b) that regarding Yom Tov, the Stam Tana is like R. Yehudah (who forbids Muktzah). We also have a Stam Mishnah like R. Shimon. And our Mishnah is better, for it is Basra! (The Gemara there cited a Stam Mishnah in Beitzah 31a that forbids Muktzah. This Mishnah of taking Peros through the hole is taught afterwards, on 31b.)

Answer #1 (Rashi, in Beitzah): Taking from where it was opened is not considered Muktzah, since it is Muktzah only due to [the Isur of] opening it, which is mid'Rabanan, for we establish it to discuss arranged bricks.

Support: We say in Beitzah (34b) that Tevel is considered prepared regarding Shabbos, since if he transgressed and fixed (tithed) it, it is fixed;

Inference: It is not considered Muktzah, since there is no Isur mid'Oraisa on it.

Answer #2: This is not considered Stam, because it could not teach 'this is R. Shimon's opinion', for perhaps R. Shimon holds that one may open l'Chatchilah, like R. Meir;

However, the Mishnah in Shabbos (156b) "we cut gourds [in front of an animal]', which could have taught 'this is R. Shimon's opinion', and it did not say so, it is surely considered Stam.

Implied question: He could have established it like Rebbi. [Breaking open] these arranged bricks is only an Isur mid'Rabanan, like it says in Beitzah (31b) "since he arranged them, he took his mind off [what is inside] them"!

Answer #1: He prefers to establish it like Rabanan, like Rava above, who establishes the Seifa like Rabanan.

Answer #2: If so, the reason of R. Eliezer, who forbids, would be because he holds like Rabanan. [R. Zeira] did not want to establish the argument [of Rabanan and R. Eliezer] like that of Rebbi and Rabanan.