Mishnah 8. This mishnah deals with someone holding a promissory note against his fellow, where the date of payment recorded in the note has already passed. The borrower claims that he already repaid the loan and received a receipt, only that the receipt was lost - and even so, he has support for his claim: it turns out that in the meantime, after the date of the loan's repayment had already arrived, the lender sold him a field and received payment for it in cash. The lender did not hold on to the money and did not say, "My time to collect has arrived, use this money to pay your debt" - and from here there is seemingly proof that the loan has already been repaid.
The case in the mishnah:
A person produces a promissory note against his fellow and claims that his fellow owes him money, and the date for repayment of the debt has already passed. The borrower, for his part, shows that after the date of repayment passed the lender sold him a field, and he argues: "If I still owed you the money and had not repaid it, you should have collected your debt at the time you sold me the field" - for from the moment the borrower handed over the price of the field, the lender should have seized that money against the loan rather than selling him a field.
The dispute between Admon and the Sages:
The lender responds that he acted with wisdom precisely: he sold the borrower a plot of land so that he would be able to take this land as a pledge and security for his debt. For as long as the borrower has nothing but cash, there is reason to fear that he will hide his money and there will be nothing from which to collect, and he will be able to evade payment and conceal the coins. But once he owns a field, he cannot hide it, and the lender will be able to collect from it in practice.
The Gemara's explanation - it all depends on the local custom:
The Gemara explains that this dispute depends on the custom of the place where the transaction is carried out:
A place where the bill of sale is written after the money is handed over: Here the Sages agree with Admon that the borrower has the upper hand. For once the lender received the price of the field first, he should have kept hold of the money and said, "I am not writing you a document for this field, since with the money you gave me I am collecting my debt."
A place where the bill of sale is written first, and only after it is handed over is the money given: In this case Admon and the Sages disagree.
Admon's view: Even though the lender must hand over the bill of sale before he receives the money, he still should have issued a declaration - to state before witnesses that he is selling him the field only so that he will be able to take it as a pledge and security. And since he did not do so, and there are no witnesses who testify that he made such a declaration before he handed over the document, the borrower has the upper hand, and he certainly repaid the loan. For if not, the lender should have said before witnesses, "Know that he still owes me the money, and I am doing this only in order to collect."
The Sages' view: The lender has a valid excuse for why he did not say these things before witnesses, because "chaver chaver yesh lo" - every person has a friend, and if the lender had made such a declaration before witnesses, word of it would eventually reach the borrower's ears, and he would withdraw from the transaction and not buy the field, for he would say, "I know what he intends to do here - to use this field in order to collect." It emerges that there is sufficient reason why he did not issue a declaration, and since there is no expectation that he issue a declaration, the lender has a good excuse for why he sold him the land. Therefore the sale provides no support whatsoever for the borrower's claim, and the lender says to him, "You did not repay the loan, and I sold you the field only so that I would be able to take it as a pledge and security."
In summary: In this mishnah we learned that according to Admon, the sale of the field after the date of repayment supports the borrower's claim that he already paid his debt, since the lender should have issued a declaration before witnesses; whereas according to the Sages the sale is no proof at all, since the lender sold him the field so that it would serve him as a security that cannot be hidden, and he did not issue a declaration out of concern that "chaver chaver yesh lo" and word would reach the borrower's ears and he would cancel the transaction. It all depends on the local custom: in a place where the money is given before the document, the Sages agree with Admon.