Our Gemara introduces a ruling made by the amora Shmuel, that if someone lends money to another person then sells the promissory note to a third party, he still retains the right to forgive the loan. Although the Gemara concludes that the individual who purchased the note – and, presumably the obligation – can return to the seller and demand a refund, nevertheless this ruling demands an explanation.
Several approaches are put forward by the rishonim and commentaries. According to the Rambam, the entire concept of selling the note is a rabbinic enactment, so the true biblical obligation remains in the hands of the original lender, who therefore retains the right to announce that he forgives the loan. Once the biblical obligation is removed, the purchaser has no claim to collect. The Ra’avad offers a different approach, arguing that the borrower has no obligation to the man who purchased the note; his sole obligation is to pay back the person who lent him the money, no matter who is holding the note. Thus, if the original agreement clearly stated that the borrower would pay back the lender or anyone else who the lender appoints or transfers the loan to, the lender would not be able to forgive payment. The Sefer Hashlama takes the Ra’avad’s approach one step further and says that even if the lender did not forgive the loan, the person who purchased the note would not be able to collect the loan directly, rather he can only ask the lender to demand payment on his behalf.
As noted, the Gemara concludes that if the lender forgives the loan, the individual who purchased the note can return to him and demand a refund. In such a case, the rishonim disagree as to whether the lender will be obligated to pay the entire value of the loan or if he will only have to refund the money that was paid for the note.