Does lawful money that is added to an interest-bearing bank account and mixes with the usurious increase become entirely unlawful?

Usurious benefits are forbidden, and a Muslim must dispose of them if they have placed their money in usurious banks. As for the principal, it is permissible for them. If a servant repents from an ongoing usurious transaction, they are to take only their principal and leave the usurious increase. If they have received the value of the usurious transaction along with its profit, they own only their original principal and should spend the usurious profit on charitable causes. The money that the father placed for his children in the usurious bank is permissible for them, and only the interest must be disposed of.