Lending money and making a stipulation

Q: A person borrowed a Sa` (1 Sa`=3 kg. Approx.) of wheat from another person at the beginning of year 1401 A.H. At that time, the wheat Sa` equaled one hundred Riyals for example. Both parties agreed on returning this Sa` after one year. When the time of returning the wheat became due, the price of a wheat Sa` increased to one hundred and thirty Riyals on the market. In this case, is the borrower supposed to return what equals only one hundred Riyals of wheat to the lender at the end of the year; bearing in mind that the amount would be less than one Sa`? Is the borrower supposed to give the lender a Sa` of wheat which would cost him one hundred and thirty Riyals, knowing that at the time of loan the price of a Sa` of wheat only equaled one hundred Riyals? Is the difference in price (thirty Riyals) considered Riba (usury/ interest)? Is it permissible for the borrower to give the lender a sum of one hundred and thirty Riyals instead of giving him/her a Sa` of wheat, if the lender does not object to this?

A: First: The borrower must return what he has borrowed on the agreed upon date to the lender, or any family representative, whether there is a price increase or decrease. Second: There is no harm in paying the debt in money, even if it is more than the original borrowed amount, as long as there is mutual consent between the lender and the borrower (at the time of repayment) and as long as there is no previous plan to do this at the time of borrowing. When there is mutual consent on the amount, it must be paid immediately (Part No. 14; Page No. 143) so as not to be considered as selling a debt for debt. May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.