65:13 If an object has a known market price, it is forbidden to sell this thing for more than that price in exchange for deferring payment. If an item does not have a known market price, one may charge a little more in exchange for deferred payment. This is permitted, even though he would accept less money if the buyer paid now, so long as he does not charge an increase in price of more than one-sixth. More than this would make it obvious that it is a fee for deferred payment and not a normal difference in negotiating the price. Even in the case of a small increase, one may not explicitly say something like, "It costs ten if you pay me now and eleven if you pay me later." Also, one may not buy goods at a high price in order to sell immediately at a loss so that he will then have the money in hand for a period of time.
65:14 If one person has a promissory note obligating another, he may sell it to a third party for less than face value, even before its due date. The one selling the note should write, "I am selling you this note, which you purchase with all its rights." The buyer of the note must accept all responsibility, except those responsibilities that remain with the seller, such as that the note has not yet been paid. Just like the holder of the note may sell it to a third party for less than its value, he may also sell it to the borrower himself.