What is the ruling on disposing of a sum of money deposited in a usurious bank unknowingly, given that its origin may involve usury, and its owner cannot be contacted? Is it sufficient to donate from it whatever is easy to give, despite the need for the money? Do charity and zakat purify acquired money that has the suspicion of usury? Is it permissible to buy and sell goods with non-Muslims?

The benefits accrued from depositing money in a usurious bank are forbidden wealth (mal haram (definition)), and one must dispose of them by spending them on theses for Muslims or by giving them to the poor and needy. It is permissible for you to take them for yourself if you are poor and in need, as mentioned by An-Nawawi. Zakat (definition) is obligatory on the principal amount if it reaches the nisab (definition) (threshold) and a full year has passed on it. As for usurious benefits, there is no zakat on them; rather, they are disposed of to get rid of them. Dealing with disbelievers in buying and selling is permissible, as the Prophet, peace and blessings be upon him, and his Companions did.