What are the consequences of swearing an oath to repay a debt that the creditor has already forgiven the debtor, and is expiation (kaffarah) obligatory?

Scholars have differed concerning one who swore to repay their debtor, and then the creditor gifted the debt to them, and they accepted it. Does the oath break merely upon acceptance, or does it only break if the due date arrives and they have not repaid it?

Some scholars hold that the oath breaks merely upon accepting the gift due to the non-fulfillment of the repayment. Asbagh and Ibn Habib subscribed to this view. Others hold that the oath does not break unless the due date arrives and they have not repaid it. This is the apparent opinion of Malik and Ashhab.

Based on this difference, it is more cautious for the questioner to repay the creditor if the due date has not arrived; otherwise, they should offer expiation for their oath as a precaution.