Is it permissible to stipulate that the loan be repaid with an amount equivalent to its value in gold at the time of repayment, in anticipation of changes in currency value?

Whoever borrows a sum of money is only obliged to repay an equivalent amount, regardless of changes in its value. It is impermissible to link its repayment to gold or silver to protect its value. The principle in repaying debts is based on the equivalent amount, not on the value, and it is not permissible to link debts to price levels. Therefore, you are not permitted to stipulate such a condition. You must repent and take only the amount you paid, in accordance with His Almighty's saying: "And if you repent, you will have your principal sums. Do not wrong and you will not be wronged."