Hawzah News Agency– A Muslim took a loan from another Muslim. After a while the market value of that amount goes down. How much should he pay back to the creditor? The amount that he got as loan or its equivalent in the market value at the time of payment? Does the rule differ if the creditor is non-Muslim?
Answer: He has to pay the same amount that he got as loan; and there is no difference whether the creditor was Muslim or non-Muslim.
Source: https://www.sistani.org/