What is the ruling on an inheritance that includes agricultural land, an unknown source of cash, and financial sums and investment certificates mixed with usury, knowing that the deceased did not pay zakat on his wealth throughout his life? Is it obligatory to purify the wealth from usurious gains despite the difficulty of tracing them? And what is the ruling on a high-value investment certificate that profited from another usurious certificate two years before the death of the deceased?

It is forbidden to deposit money in usurious banks and to benefit from prohibited interest; rather, one must dispose of it. If the person who acquired illicit wealth dies, what was inherently forbidden (like stolen goods) is not permissible for the heirs. However, what was forbidden due to its acquisition (like usury) becomes permissible for the heirs, and they are not obliged to dispose of it. The heirs must pay zakat on behalf of their father for the past years, based on their best judgment. As for the money found in the house whose duration of presence is unknown, the default is that no zakat is due on it unless a full year has passed. It is good to pay zakat on it as a precautionary measure, with the consent of the adult heirs.