What should we do now that my husband has engaged in a usurious transaction with the bank to purchase a car, without knowing it was forbidden, and what is the expiation and punishment for this act, and does his ignorance of it and lack of intention to deal in usury exempt him from sin?

The transaction mentioned could be a valid sale with deferred payment, with the debt then sold to the bank, in which case the sin would be on the company, not on the husband. Or it could be an interest-based loan from the bank. If the husband was unaware and the company deluded him into believing it was a true installment sale, we hope he is excused.

There is no harm in benefiting from the car, and there is no need to sell it or expedite payment to the bank if the usurious interest is not waived.

We alert those who transfer their salary to an interest-based bank or where no Islamic banks exist, to suffice with opening only a current account, and not to leave money in it except out of necessity, estimated according to its extent.