445. Extending the Loan in Exchange for a Favor

65:3 Let’s say that the parties did not arrange for interest at the time of the transaction but rather one lent the other money for free until a certain time, or that one party sold the other some goods with payment deferred until a certain time, or that one party owes money to another no matter how the debt came about. If the time to pay arrives and the parties agree on a deal to extend the time in exchange for some consideration, this is also interest.

65:4 If the borrower repaid the lender more than he owed, even though there was no agreement obligating him to do so, and even though he did not state that he is giving him the extra money as interest, nevertheless it is prohibited.