Is there an issue of ribbis, if my friend uses my credit card, and pays me back in cash right away. However, by using my credit card, my friend is causing me to accrue miles. Do we consider my friend to be called a “borrower” from me, and do we consider that which he causes me to receive miles, as if he is giving back extra for lending him money.
It isn’t ribbis for a number of reasons. Firstly the benefit of the miles is not because he lent you the money, but because he gave the credit card business. Secondly the payment is not coming from the borrower to the lender, rather from the credit card company to the lender.