How are the deceased's usurious funds purified if the exact amount cannot be precisely determined, and will the deceased be tormented for bank interest that they did not know was usury, even if the estimated amount is given in charity?

The children of the deceased must extract the usurious gains from his wealth and spend them on charitable causes after identifying the origin of the deposit and requesting a statement from the bank that clarifies this. We pray for the deceased's forgiveness and mercy, and this action by his children will benefit him. Therefore, they should frequently supplicate for him, as the supplication of a righteous child benefits the deceased, as stated in the Hadith.