QUESTION: The Mishnah states that when one neighbor raises, at his own expense, the dividing wall to more than four Amos high, and then the other neighbor builds a wall in his own property the same height with intention to use the dividing wall as support for a roof beam, he is obligated to pay for half of the expenses of raising the dividing wall to its present height even before he actually places his roof beam on it, because he shows that he is pleased with the addition and wants to use it for himself.

Why, though, must he actually pay for the addition to the wall even before he benefits from it? (RITVA)

Moreover, even if he does benefit from the addition to the wall, why is he obligated to pay for it? It should be a case of "Zeh Neheneh v'Zeh Lo Chaser" -- the second neighbor benefits from the addition to the wall, while the first neighbor loses nothing, in which case the Halachah is that the one who benefits does not have to pay. (TOSFOS)

What sort of obligation is this? Why must he pay before he has actually benefited?

Moreover, how does this answer the question of Tosfos, that it is a case of "Zeh Neheneh v'Zeh Lo Chaser"?

The BI'URIM V'HE'OROS cites CHIDUSHEI HA'GA'ON RAV NAFTALI TROP who answers that he is obligated to pay once it is evident that he wants the wall, because it is considered as though the neighbor who built the addition to the wall did so upon the request of the other neighbor, as his Shali'ach.

The KETZOS HA'CHOSHEN (158:6) writes that according to this explanation, the question of TOSFOS (DH Af Al Pi) is no question. Tosfos asks why the neighbor should be obligated to pay for half of the expenses if it is a case of "Zeh Neheneh v'Zeh Lo Chaser" -- the second neighbor benefits from the addition to the wall while the first neighbor loses nothing. According to these Rishonim, this is not a question. His obligation to pay is not due to the fact that he benefits from the wall (indeed, he has not yet benefited from it), but rather it is due to the fact that he acquired part of the wall through Kinyan Chatzer.

Why does Tosfos not accept this explanation? The BI'URIM V'HE'OROS suggests, based on the words of REBBI AKIVA EIGER (on the Mishnah) and CHIDUSHEI REBBI SHIMON SHKOP (4:3), that Tosfos maintains that the neighbor does not want his Chatzer to acquire part of the wall for him (for he could benefit from the wall without paying anything). Therefore, it must be that the reason why he must pay is that he is not allowed to benefit from someone else's property without paying for that benefit. Once he must pay, it is assumed that he wants to acquire his share of the wall. That is why Tosfos asks that it should be a case of "Zeh Neheneh v'Zeh Lo Chaser," and thus he should be allowed to benefit without paying and it cannot be assumed that he has intention for his Chatzer to acquire a share of the wall for him.

QUESTION: The Gemara asks a general question about the power of a "Migu" ("Mah Li l'Shaker"). When a person has a Migu but that Migu is countered by a Chazakah, does the Migu prevail or does the Chazakah prevail? The Gemara asks this question in the specific case of a lender who demands repayment of the loan after the time the loan became due, and the borrower says that he paid back the loan before the time that it was due. On one hand, the borrower has a Migu: if he is lying he would have said a better claim that certainly would have exempted him; he would have claimed that he paid after the time the loan was due (in which case a borrower is believed about a Milveh Al Peh, a loan that is not written in a Shtar). Hence, with this Migu he should prevail with his present claim that he paid before the time the loan became due. On the other hand, a Chazakah counters his Migu: there is a Chazakah that a person does not pay back a loan before it is due. Do we follow the Chazakah and require him to pay, or do we follow the Migu and exempt him from paying?

What is the Gemara's question? The Chazakah certainly is stronger than the Migu. There is a general principle that a Migu that would enable a person to extract money from someone else ("Migu l'Hotzi") is not a valid Migu. In contrast, a Chazakah that would enable a person to extract money from someone else is a valid Chazakah, as is evident from this case itself: if the lender demands repayment before payment is due, and the borrower claims that he repaid already, the Chazakah that a person does not pay back a loan before it is due determines that the borrower is not telling the truth and thus the lender can extract money from him based on this Chazakah. Why, then, is there any question about whether a Migu is stronger or whether a Chazakah is stronger? A Chazakah certainly is stronger because it may be used to extract money! (SHITAH MEKUBETZES)

According to this explanation, there are two ways of understanding the Gemara's question about whether a Migu (combined with a Chezkas Mamon) overrides a Chazakah. The Gemara might be asking whether the borrower's Migu actually combines with the borrower's Chezkas Mamon to give the borrower's claim the added strength of two powers -- that of a Migu and that of a Chezkas Mamon. On the other hand, perhaps the two do not combine, because the nature of how they work differs. A Migu works because it clarifies (to some degree) what actually happened; it gives credence to the person's claim that he is the rightful owner of the money (for, if he wanted to lie, he would have said a bigger, more effective lie), suggesting that what he claims is indeed what happened. In contrast, a Chezkas Mamon does not clarify the issue in question. Rather, it merely says that in lieu of any proof, Beis Din cannot extract money from the person presently in possession of it. It does not suggest that the person with the Chezkas Mamon is the rightful owner. Therefore, perhaps the two do not combine with each other to give the borrower's claim added power. (See BI'URIM V'HE'OROS.)

A second way to understand the Gemara's question is that even though a Chazakah is stronger than a Migu alone, the Migu (with a Chezkas Mamon) perhaps serves to weaken the power of the Chazakah; the Migu that lends credence to the borrower's claim that he paid back the debt weakens the Chazakah that people do not pay back debts before they are due. The Gemara is asking whether or not a weakened Chazakah still enables a person to extract money from someone else. (See BI'URIM V'HE'OROS.)

The BI'URIM V'HE'OROS quotes the AVNEI NEZER (EH 42), who cites the SHACH (CM 108:7; see also KETZOS HA'CHOSHEN 108:4) who explains that the Gemara is not referring to a normal type of Migu, where there is reason to believe the claimant because if he were lying, he would have said a better lie. Rather, it is referring to a stronger type of Migu, the Migu of "ha'Peh she'Asar Hu ha'Peh she'Hitir" (see Insights to Yevamos 119:1, end of answer (a)) -- had the claimant did made any claim, he would have prevailed. By making a claim, he created a reason not to believe him, and therefore Beis Din accepts the rest of his claim that he is the rightful owner of the money. In this case, there are two parts to the borrower's claim: first, that he repaid, and second, that he repaid before the loan was due. He did not need to say the second part, that he repaid before the loan was due. By saying that he paid back before it was due, it is like "Peh she'Asar Hu ha'Peh she'Hitir."

The Shach, however, seems to retract this answer. He says that a "Peh she'Asar" type of Migu is also not able to override a Chazakah. Moreover, if the Migu in this case is a "Peh she'Asar," then the questions of Tosfos here would not be questions.

(The MAHARIT (Teshuvos, Even ha'Ezer #276), TERUMAS HA'DESHEN (#207), and REBBI AKIVA EIGER (Teshuvos #136) also write that if this Chazakah is stronger than a Migu, it is because it is an "Anan Sahadei" with the strength of witnesses. See BI'URIM V'HE'OROS, #75 and #85.)