Or perhaps where there is a presumption against a person’s claim, we do not say that the borrower can claim: Why would I lie? The Gemara suggests: Come and hear a proof from the mishna: If after the wall was built one of the neighbors claims he alone constructed it and the other did not participate in its building, the latter is nevertheless presumed to have given his share of the money, unless the claimant brings proof that the other did not give his share.

The Gemara clarifies the matter: What are the circumstances of the case? If we say that one partner demanded that the other party pay the money after the time that the payment became due, i.e., after the wall was rebuilt, and the other partner said to him: I paid you at the time that the payment became due, it is obvious that he is presumed to have given him the money. Rather, is it not a case where he said to him: I paid you within the time, i.e., before the payment became due? Apparently, even where there is a presumption against a person’s claim, we say that the defendant can claim: Why would I lie? The Gemara rejects this proof: Here it is different, because the time to pay is upon the completion of each and every row. Therefore, it is as if he said: I paid you at the time that the payment became due.

The Gemara suggests: Come and hear another proof from the continuation of the mishna. The court does not obligate the reluctant neighbor to contribute to the building of the part of the wall that is above four cubits. But if the reluctant neighbor built another wall close to the wall that was built higher than four cubits, in order to set a roof over the room that was thereby created, the court imposes upon him the responsibility to pay his share for all of the rebuilt wall, even though he has not yet set a roof over it. If the builder of the first wall later claims that he did not receive payment from his neighbor, the neighbor is presumed not to have given his share of the money, unless he brings proof that he did in fact give money for the building of the wall.

The Gemara clarifies: What are the circumstances of the case? If we say that one partner demanded that the other party pay the money after the time that the payment became due, and he, the latter, said to him: I paid you at the time that the payment became due, why is he not deemed credible? Rather, is it not that he said: I paid you within the time, before the payment became due? And with regard to this case, the mishna states that he is not deemed credible. Apparently, where there is a presumption against a person’s claim, we do not say that the defendant can claim: Why would I lie? The Gemara rejects this proof: Here it is different, since the reluctant neighbor says: Who says that the Rabbis will obligate me to pay for this additional part of the wall? In such a case he certainly does not pay before the payment becomes due. The mishna does not provide a proof one way or the other.

Rav Aḥa, son of Rava, said to Rav Ashi: Come and hear a proof from what is taught in a mishna (Shevuot 38b): If one said to another: I have one hundred dinars in your possession, and the other one said to him in the presence of witnesses: Yes, that is so; and the next day the lender said to the borrower: Give me the money that you owe me, the halakha is as follows: If the borrower said: I already gave it to you, he is exempt. But if he said: Nothing of yours is in my possession, he is liable.

The Gemara clarifies the matter: What, is it not that when he says: I already gave it to you, he is saying to him: I repaid you at the time that the payment became due; and when he says: Nothing of yours is in my possession, he is saying to him: I repaid you within the time, before the payment became due? And yet, the mishna teaches with regard to the latter case that he is liable. Apparently, where there is a presumption against a person’s claim, we do not say that the borrower can claim: Why would I lie? The Gemara rejects this proof: No, what does he mean when he says: Nothing of yours is in my possession? He is saying: There were never such matters; i.e., the purported loan never occurred. As the Master says: Anyone who says: I did not borrow, is treated as one who says: I did not repay, and since it is known by his own admission that he borrowed money, he is liable to pay.

§ The mishna teaches: But if the reluctant neighbor built another wall close to the wall that was built higher than four cubits, in order to set a roof over the room that was thereby created, the court imposes upon him the responsibility to pay his share for all of the rebuilt wall. Rav Huna says: If he built another wall close to the first wall that was half the length or the height of the wall that was built higher than four cubits, it is as if he built it close to the height and length of the entire wall. Since he can easily add to his wall so that it will be equal in length or height to the wall the neighbor rebuilt, he must therefore pay half the cost of the entire rebuilt wall. And Rav Naḥman says: With regard to that which he built close, he built it close; with regard to that which he did not build close, he did not yet build it close. Accordingly, he is required to pay an additional share only for the part of the wall corresponding to the new wall he built.

And Rav Huna concedes with regard to an attachment to the corner of his house that he is not required to pay half the cost of the entire rebuilt wall. If he built the extension of his house in this manner, it is not considered as if he built it close to the entire wall, as it is unlikely that he will add to it. And Rav Naḥman concedes that in a case in which he places a heavy beam [be’afriza] on the wall that can support a roof, or carves into the wall indentations to fix beams in place, then even if he has not yet made use of the entire height of the wall, he has demonstrated his desire to do so in the future, and therefore he must pay half the cost of the entire wall.

§ The mishna teaches that if the builder of the first wall later claims that he did not receive payment from his neighbor, the neighbor is presumed not to have given his share of the money, unless he brings proof that he did in fact give money for the building of the wall. Rav Huna says: Even if openings in the wall were built on the side facing the reluctant partner and these openings are suited to serve as beam rests, this does not create a presumption that the reluctant partner contributed his share to the building of the wall. And this is the halakha even if the builder of the wall made sills for these openings. As the builder of the wall can say to his neighbor: I said to myself that when you will appease me and pay me for the construction of the wall, you might want to attach beams to it, and I do not want the foundations of my wall to be damaged by your fashioning new openings in it. Therefore, from the outset, I built the wall with these openings.

With regard to the use of a neighbor’s wall, Rav Naḥman says: If one acquired the privilege to place thin beams on his neighbor’s wall, i.e., if one had used the wall in that manner in the past and the owner did not protest, so the one using it can maintain that he had acquired from the owner the right to do so, he has not acquired the privilege to place thick beams there. But if he acquired the privilege to place thick beams on the wall, he has acquired the privilege to place thin beams there. Rav Yosef says: If he acquired the privilege to place thin beams, he also has acquired the privilege to place thick beams.

There are those who say that Rav Naḥman says: If one acquired the privilege to place thin beams on his neighbor’s wall, he has acquired the privilege to place thick beams there; and if he acquired the privilege to place thick beams, he has acquired the privilege to place thin beams. This version of Rav Naḥman’s statement accords with the statement of Rav Yosef.

With regard to a similar matter, Rav Naḥman says: If one acquired the privilege to let water drip from his roof into his neighbor’s courtyard, he has acquired the privilege to let the water pour there though a drainpipe. If the neighbor did not protest about the water dripping from the roof into his courtyard, he would certainly allow him to build a drainpipe, which would limit the water to a single place. But if he acquired the privilege to let the water pour through a drainpipe into his neighbor’s courtyard, he has not acquired the privilege to let water drip there from his roof. And Rav Yosef says: Even if he acquired the privilege to let water pour there through a drainpipe, he also has acquired the privilege to let water drip there from his roof.

There are those who say that Rav Naḥman said: If one acquired the privilege to let water pour through a drainpipe into his neighbor’s courtyard, he has acquired the privilege to let water drip there from his roof; and if he acquired the privilege to let water drip from his roof into his neighbor’s courtyard, he has acquired the privilege to let water pour there through a drainpipe. But he has not acquired the privilege to let water drip from a hut whose roof is composed of willow branches into his neighbor’s courtyard. Rav Yosef said: He has acquired the privilege to let water drip there even from a hut whose roof is composed of willow branches. The Gemara comments: Rav Yosef performed an action, i.e., issued a practical ruling, with regard to a hut whose roof is composed of willow branches, allowing the neighbor to let water drip from there after he had acquired the privilege to use a drainpipe.

Rav Naḥman says that Rabba bar Avuh says: If one rents a room to another