If he said to him: You are hereby prohibited to me by force of ḥerem, the one making the vow is himself prohibited to derive benefit from the addressee or from his property. If he said to him: I am hereby prohibited to you and you to me by force of ḥerem, they are both prohibited to benefit from one another. And they are permitted to benefit from anything belonging to those who come up from Babylonia, i.e., public property that is not owned by any person or group, but they are prohibited to benefit from property that is jointly owned by the inhabitants of that city, as both parties have a share in such items.

That mishna provides examples: And the following are items of those coming up from Babylonia, i.e., publicly owned items: The Temple Mount, the chambers, and the courtyards on the Temple Mount, and a cistern situated in the middle of the road. And these are items jointly owned by the inhabitants of that city: The street, and the synagogue, and the bathhouse.

Rava, having cited the mishna in full, concludes his challenge to the opinion of Rav Naḥman: And if you say that a cistern of those who come up from Babylonia, a public cistern, is owned jointly by partners, i.e., by all Jews, why should it be permitted for the one who made the vow and the addressee to use it? But didn’t we learn in a mishna (Nedarim 45b): Two partners who took a vow not to derive benefit from one another are prohibited to enter a joint courtyard in which they both have a share to wash themselves in a cistern. According to you, the same should apply to a cistern in which the two of them have a share, such as the cisterns of those who come up from Babylonia.

Rav Naḥman answered: Indeed that is the case. So too, they are prohibited to wash themselves in a cistern because when bathing one uses of all the water of the cistern, part of which belongs to the forbidden partner. But when the baraita says that a cistern of those who come up from Babylonia is permitted to both parties, with what are we dealing here? The baraita is referring only to filling water from the cistern. This is permitted because it is considered that this one fills from his portion, and that one fills from his portion. The water that each of them draws is considered retroactively designated exclusively for him, so that the partner has no share in it at all.

The Gemara asks: And does Rav Naḥman hold that there is retroactive designation? But didn’t we learn in a mishna (Shekalim 1:7): If brothers divided up inherited property among themselves and subsequently joined their property again and became partners, they are obligated to add a kalbon, a small coin, to the obligatory half-shekel yearly Temple donation. The kalbon covered both the cost to the Temple of exchanging half-shekels into larger coins and the depreciation of the donated coin. Although a whole shekel given by two partners does not need to be changed into a larger coin, the Sages imposed the same kalbon fee on the partners as on everyone else. However, these partners are exempt from the animal tithe, in accordance with the standard halakha that people who own animals in partnership are exempt from the animal tithe.

The quote from the mishna continues: And in a situation in which the brothers are liable for the animal tithe, as when they have not yet divided up their inheritance, and all the deceased’s estate is therefore still considered a single unit and not a partnership, they are exempt from the kalbon, in accordance with the halakha that a father who contributes a single shekel for his two dependent sons does not need to add the kalbon.

And Rav Anan said: The Sages taught that the inherited property is no longer considered a single unit after the brothers divided it and then rejoined in a partnership only when they divided kids against lambs or lambs against kids, i.e., if one brother took kids and the other took a corresponding value of lambs. This kind of division is considered a commercial transaction, with one brother purchasing goats and paying for them with lambs and vice versa. Therefore, when they join their animals again as partners, it is considered an entirely new partnership.

However, if they divided kids against kids and lambs against lambs, meaning that each brother took an equal portion of each of the items they inherited, one can say of each brother’s portion: This is his portion destined to reach him from the first moment, from the time of the death of the deceased. If the brothers form their partnership again, the inheritance becomes a single unit again, and they are therefore obligated in the animal tithe and exempt from the kalbon.

But Rav Naḥman said: Even if they divided kids against kids and lambs against lambs, one does not say that this is his portion destined to reach him from the first moment. This is because Rav Naḥman does not accept the principle of retroactive designation. Consequently, the resolution proposed previously for the issue of filling water from the cistern of those who come up from Babylonia is invalid.

The Gemara retracts its previous explanation of the disagreement between Rava and Rav Naḥman: Rather, everyone agrees that a cistern of those who come up from Babylonia, i.e., a public cistern, is an ownerless cistern, but here they disagree over a different issue: One who picks up a found article intending to acquire it on behalf of his friend. One Sage, Rav Naḥman, holds that if one picks up a found object on behalf of his friend, his friend acquires it through this act as though he had picked it up himself. The water of the ownerless cistern is like a found object. Therefore, if one draws water on behalf of another, the latter acquires it, and consequently the water is as his feet. And one Sage, Rav Sheshet, holds that when one picks up a found object for another, the latter does not acquire it. Rather, it belongs to the one who actually picked it up, and consequently the water is as the feet of the one who draws it.

MISHNA: With regard to one who had produce in a different city beyond the Shabbat limit, and the residents of that city where the produce was located joined the Shabbat boundaries, enabling them to reach the owner’s home on the Festival, and they wish to bring him some of his produce, they may not bring it to him. His produce is as his feet; since it is outside of his Shabbat limit, it may not be taken from its place. However, if the owner placed an eiruv to enable travel to that city, the legal status of his produce is like his status with regard to the Shabbat limit. People from that city who also placed an eiruv may bring the produce to him, since he himself may walk to the produce and take it.