What is the ruling on a merchant selling goods on credit, then requesting payment for their price in another currency (such as the dollar or the euro) instead of the dinar agreed upon at the time of sale, due to price changes, with the consent of both parties?

It is not permissible to sell goods on credit in dinars with the condition that payment be made in another currency, such as dollars. However, it is permissible to accept their value in dollars at the time of payment if there was no prior condition at the time of the contract, provided that it is at the prevailing rate of that day. It is not permissible to accept another currency in exchange for a debt unless the exchange takes place in the same session, because this is considered a currency exchange (sarf), which requires immediate mutual possession. The correct method is to price the goods and sell them directly in the currency one wishes to obtain.