Ahsan Allahu Ilaykum, I earned some money in cash and gave it to my father in order to make an online purchase for the same amount using his credit card. My father does not pay riba, but I believe it is included in the contract for this card. Was this a sinful act? BarakAllahu feekum Ustadhna

Using a card that does not involve a contract of riba always takes precedence. Of course, there is a lot of information missing here: 1. Is this something that is necessary? 2. Are there other ways? 3. Are there truly no alternatives? However, take it as a rule of thumb: always use something that is free of suspicion.