Thank you for your help.
A person gives tzedaka via a payment on their own credit card and earns points from their card issuer on the purchase. The card holder then redeems these points for cash back to their bank account or a credit card statement credit. Would there be any issue of ribbis by doing this?
There is no issue of ribbis here, and it is permitted. The reason is because there was no loan given to anyone here. You gave tzedakah and used the card, the same way you use it for making any other purchase, and it isn’t ribbis. Even in a case where you would have put used your card to give tzedakah for someone else, and you did give them a loan, you would be able to benefit from the points that are accrued to your card. This is because the person who used your card, who is the person to whom you lent the money, is not the person who got the loan.
Another point, the fact that the credit card company is giving you points for purchases is not ribbis, because when you charge your credit card, you are now borrowing money from the credit card company. Which makes them the lender and you the borrower. If the lender gives the person who borrowed money a present that is not ribbis. It is only when the borrower, gives the person who lent him the money something extra, but not the other way around.