I have a mudaarabah savings account in an Islamic bank, and my father has an interest-free savings account in an interest-based bank. My father gives me a certain amount of money to deposit in my account. After some days, however, he asks me to withdraw the money from my account and also asks me to go and deposit the money in his own account in the interest-based bank. When I told him that I cannot do this, he told me that our driver will do the job then. If I withdraw the money from my account in the Islamic bank and on my way home we stop by the interest-based bank and the driver goes inside to deposit the money while I wait inside the car in order to guard it, will this still be regarded as me having helped to deposit the money in the interest-based bank account? Will I be sinful?

All perfect praise be to Allaah, The Lord of the worlds. I testify that there is none worthy of worship except Allaah and that Muhammad is His slave and Messenger.

You are not sinful for waiting in the car for the driver to deposit the money in your father's account in an interest-based bank.

You should advise your father in a gentle, wise manner to stop dealing with an interest-based bank, even if his dealing did not result in any interest because by just depositing money in the bank, the bank benefits from it, and this is considered helping it. Allaah says (what means): {…but do not cooperate in sin and aggression.} [Quran 5:2]

There is no need for that while there are legitimate alternatives, such as Islamic banks.

The Fatwa of the Standing Committee for Iftaa' reads:

"If the bank benefits from the money deposited in it by using it in interest-based transactions, and the owner of the money is able to save his money from thieves and the like in other ways that do not involve interest, then it is prohibited for him to deposit his money in the bank and the like, which will use it in forbidden transactions and violations of Islam. A means that leads to committing evil is evil, and helping in committing what is prohibited is prohibited; indeed, the means have the same ruling as the ends."

Allaah knows best.