a husband asks his wife to deposit her money in an islamic bank, but she refuses, to what extent is he involved in this sin? what does he do?

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, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.

If you mean that the wife wants to deposit her money in a usurious bank, this is not permissible for her, and her husband has to prevent her from doing that. By giving her advice, the husband has done his duty. If the woman has already deposited her money in a usurious bank, she must first repent to Allaah, then withdraw the money from the bank. If the money has earned a profit, she has to spend the profit in charitable channels with the intention to dispose of the ill-gotten money. After that, she may deposit it in an Islamic bank or keep it with her if she does not fear losing it.

Finally, the husband should continue to advise her in a kind manner. It is disliked that for him to use her money if it is a mixture of lawful and unlawful money, yet he is forbidden to use her money if it is purely unlawful. For further information, see Fatwa 90054.

Allaah Knows best.