There are indeed potential halachic issues with borrowing or lending a credit card since it is forbidden to charge interest from your fellow Jew.

To help clarify things, let’s give a simple and common scenario: You went shopping with a friend, who either left her wallet at home or is a bit cash-strapped at the moment. Being a good friend, you offer to let her use your credit card, figuring that it will be a win-win for both of you. Your friend gets to make her purchase and you get to rack up some points on your credit card toward a well-deserved vacation.

Interest

Before you reach for your wallet, the following must be clarified. According to halachah, when you let someone use your credit card, you are borrowing the money from the credit card issuer and in turn lending the money to your friend. In other words, there are really two transactions taking place, one between you and the bank, and another between you and your friend.1

Now, according to Jewish law, although a Jew is permitted to borrow money and pay interest (ribit) on a loan from a non-Jew, a Jew is forbidden to be party to any transaction that involves charging another Jew interest.2

Practically, this means that if your friend is cash-strapped and plans on paying you back in installments, compensating you for any interest or late fees3 you may incur, even if your friend is more than happy and willing, she is not allowed to pay even a penny more than the original charge. This applies even if it is arranged that she pay the money directly to your credit card issuer.4

The above is not meant to discourage you from lending money to one in need. On the contrary, lending money to someone in need is considered a very special mitzvah and one of the greatest forms of charity.5 However, when giving your credit card to use, you need to be very aware that you are actually lending your own personal money, not the bank’s.

Therefore, if your friend isn’t able to pay you back the full amount by the due date, you either need to take upon yourself to pay any interest or late fees that are incurred with your own money, or just pay off the full amount on the credit card bill from your own personal money, and your friend will pay you back the loan amount over time.

Points, Miles and Cash Back

We can now turn to the original question about points, miles or cash back off someone else’s use of your credit card.

As we explained, there are essentially two transactions taking place. When the bank or credit card issuer gives you a “reward” for using their card, it is a gift from them, not your friend, and therefore permitted. This is akin to the rule that one person may reward another person to lend a third person money (provided that the borrower didn’t direct the gift-giver to do so).6

It should be stressed, however, that just because something may be halachically permissible, does not necessarily mean that it is financially wise or legal to do so. Lending one’s credit card just to earn points is usually a bad idea, and people may lose thousands of dollars when the borrower is unable to pay them back in a timely manner.

At the same time, giving an interest-free loan (in an above-board and responsible manner) is one of the greatest mitzvahs. The Torah associates being careful about the mitzvah of ribit (interest) with G‑d’s taking the Jews of Egypt.7 The mystics tell us that when we are careful with the mitzvah of ribit and give interest-free loans, G‑d becomes a partner in our endeavors, ensuring that they be successful and full of blessings, and we merit that he takes us out of our “personal Egypt” and ultimately out of this final exile.8 May it be speedily in our days!