Is it obligatory to repay a debt at its current value, which is equivalent to its purchasing power at the time of borrowing, or at its original nominal value?

The borrower must return what he borrowed without any increase due to changes in currency value or rising prices. However, if he voluntarily gives an increase without a prior condition, this is permissible and is a commendable act of kindness in Islamic law, for the Prophet, peace and blessings be upon him, said: "The best among you are those who are best in paying off debts."