Explanation (R. Chananel): The Siman is "Bava Sha'ar Tara Sha'ar." I.e. R. Yehudah ben Bava permits slaves. "Bava" and "Tara" both refer to a Sha'ar (gate).

Note: Before this, R. Chananel wrote "why does R. Yehudah ben Bava permit slaves and forbid wives? Because [slaves] dwell at the doorway of their masters, and it is as if the place of their eating and sleeping is there." It seems that his text said so.

Explanation: [R. Chananel explains that Rav] brings the verse for a Siman and reason for his words.

Implied question: Abaye knew the Beraisa above (72b, which says that if five members of a Chatzer were Me'arev, one of them can take the Eruv elsewhere)! Above (49b), he challenged Rabah from it. He said "it is difficult for you, and difficult for Shmuel" regarding "Eruv is due to Kinyan."

Answer: Here, he asked Rabah [even though he knew that Rabah will answer like the Beraisa says] only in order to challenge him from our Mishnah.

Explanation #1 (Rashi): This refers to two Chatzeros one inside the other. A Mishnah below (75a) teaches that if they are of individuals, they need not be Me'arev;

[Rami bar Chama] asks, if a father and his son live in the inner [Chatzer], are they considered like individuals, or a Rabim?

Question (Ri): We learn this from our Mishnah! It is proven that a father and his son do not forbid each other;

Since they do not forbid each other, if so, this is [a Chatzer with Drisas ha']Regel that is permitted in its place, and it does not forbid outside its place. This is the reason why individuals need not be Me'arev!

Answer: He asks about when they receive Pras (food, or money for food). He is unsure whether our Mishnah discusses [sons] who literally eat on their father's table, and there they need not be Me'arev when there are no [other] residents with them. It helps a little that they eat [his] bread, even though the place of lodging determines;

However, if they receive Pras (food, or money for food, and eat it in their place), even if there are no [other] residents with them, they must be Me'arev.

Or, perhaps our Mishnah discusses [sons] who receive Pras, like Rav established it (72b), who said there that the place of bread determines.

[Rav Chisda] brought a proof from the Beraisa, for a Stam father and his children, or a Rebbi and his Talmidim, receive Pras, since they sleep in their houses, where it did not teach explicitly "they eat on their father's table."

Rebuttal: It does not connote like this at all to say so!

Explanation #2 (Ri): He asks when in the entire Mavuy there are only a father and his son, or a Rebbi and his Talmid. Their houses and Chatzeros open to the Mavuy. Perhaps since the entire Mavuy is theirs, the law of Eruv will be forgotten;

He asks also, if you will say that they need not be Me'arev, is their Mavuy permitted through a Lechi or Korah, or not?

Implied question: There is an opinion above (71b) that with bread, all agree [that Shituf suffices. If so, this is not only like Rabanan!]

Answer: It connotes to him that "if they did Shituf in the Mavuy" is in any way, even if they did Shituf in the Mavuy with wine. (Only Rabanan hold that this suffices.)

Question: According to the opinion that one cannot be Mevatel from Chatzer to Chatzer, why are they permitted in the Mavuy?

He cannot be Mevatel his Reshus to the members of another Chatzer according to Rava, who says that according to Shmuel, two Chatzeros one inside the other, sometimes they cannot be Mevatel!

Answer: This is not difficult. He joined Shituf in the Mavuy!

Question: The following is difficult. How does Bitul help in the Mavuy according to Rava? He said that two Chatzeros, one inside the other, cannot be Mevatel!

You are forced to say that there is Bitul Reshus in a Mavuy, like [the Gemara] deduced, since [the Mishnah] taught "he was Mevatel his Reshus to them"!

Answer: Since all of them are equal in the Mavuy, this one like this one, he can be Mevatel even to the members of another Chatzer, for the Mavuy is one use for both of them;

This is unlike two Chatzeros, for this one's use is alone, and this one's use is alone, like it says above (66b. There is more reason to say that Bitul helps for a ruin between two houses, for both use it together, than for two Chatzeros.)

Support: [Also] below (79a), a Beraisa teaches that if a house was between two Chatzeros and they filled it with straw, if the straw diminished from 10 Tefachim, they can be Mevatel the house to this and to this;

The reason is like I explained, that even according to Shmuel, the house to the Chatzeros is one use for both of them;

Explanation (Rashi): This is why Rav did not teach that they are open to each other, for he is concerned lest they bring it in through the openings between them.

Inference: If they are open to each other, Shituf does not help, even if they bring it in through the Mavuy. We decree lest they rather bring it in through the opening of the Chatzer, and rely on it.

Question: How do we find an argument of R. Meir and Rabanan about Me'arvin and Mishtatfim, if not when Chatzeros open to each other? It connotes there that Shituf helps!

Answer: We find it when the Chatzeros were Me'arev through windows;

Since there is not a proper opening from Chatzer to Chatzer 10 [Tefachim] tall and four [Tefachim] wide, we do not decree lest they take out and bring in the Shituf not through the Mavuy, since one cannot take plainly from Chatzer to Chatzer if there are not openings, rather, mere windows.

Explanation (Rashi): He brought the barrel in all the Chatzeros, and from them to the Mavuy, and from there to the Chatzer in which it was placed, and not for the sake of Shituf.

Question #1: According to his Perush, it should have said "he brought it in, took it out and brought it in"!

Question #2: There was no need to say this difficult Perush, that first it was in other Chatzeros, and he took it out to the Mavuy, and brought it into this Chatzer!

Observation: Here it is not relevant to say "he took it out and brought it in." (Therefore, it is difficult for Rav Yosef why they may rely on the food.)

Implied question: He could say that each one brought a loaf into this Chatzer through the Mavuy in order to eat!

Answer: Normally, the owner of the barrel invited them to eat by him. Even though he was not Mezakeh, we rely on bread on the table. It is as if they acquired it.

Suggestion: Perhaps it occurred that the bread of the Ba'al ha'Bayis was in the other Chatzeros, and it was brought to here through the Mavuy!

Rejection: This taking out and bringing in would not help at all, since the bread was not acquired to all people of the group at that time. Rather, it was of this Ba'al ha'Bayis;

Taking out and bringing in helps if at that time it belonged to the participants in the Shituf.