Bava Batra 168 - Partial Debt Payments
One repaid part of his debt. The borrower and lender did not want to go through the trouble of writing a receipt. By right, the lender should keep the loan document, but the borrower was afraid that the lender would dishonestly collect the entire loan again. Therefore, they deposited the loan document with a third party.
The lender then said to the third party, "If I don't pay the balance by such-and-such date, give the document to the lender" - meaning that he forfeits the partial payment. In the end he did not pay. Rabbi Yossi says that the third party should give the loan document to the lender. Rabbi Yehudah says that he should not give it back, because the borrower never really meant it.
After much deliberation the law is not like Rabbi Yossi - promises like this one are not binding.
Art: Jan van Ravesteyn - Pieter van Veen, his son Cornelis and his clerk Hendrick Borsman