My sister sold her business and has received a large sum of money, which my father is safeguarding in his bank as my sister is living abroad. My question is will my sister be held responsible for the interest that my father accepts from her money? She has warned him not to accept the interest and has shown her disapproval, but he still insists on taking the interest.

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. We ask Allaah to exalt his mention as well as that of his family and all his companions.

First of all, it is forbidden to save money in banks which deal with Ribaa (interest and usury) unless one fears for his money to be stolen or lost and there is no Islamic bank to save money in. In this case, the customer is obliged to save his money in a current account which does not procure Ribaa, as a means of doing the lesser of two evils. However, if one is obliged to save his money in a saving account, then he should spend the interest [Ribaa] in the Muslim public welfare with the intention of getting rid of forbidden money, like spending it on orphanages, schools and hospitals. Indeed, this is detailed in Fatwa 84007, so please refer to it.

Therefore, the questioner is obliged to get rid of the interests [Ribaa] or she should ask her father to do so. If he does so, then this is what is required, otherwise she should not take anything from this interest and it is her father who is sinful.  

Allaah Knows best.