Is it forbidden to pay interest on loans due to inflation?

It is forbidden to pay interest on loans, even due to inflation. Scholars have agreed that a loan which stipulates repayment with an increase is forbidden usury (riba). The borrower must repay the equivalent amount of money they borrowed, regardless of the currency's value on the day of repayment. Imam Ahmad, however, made an exception in the case where the ruler prohibits dealing in the borrowed currency; in such a situation, the borrower should value the loan on the day it was taken and repay it in the new currency, because prohibiting its use renders it valueless.