What is the ruling on benefiting from the usurious returns of investment certificates, especially since the mother insists on using them to cover study expenses and needs, despite the son's knowledge of their prohibition?

Money must be withdrawn from the investment account that yields usurious profits, and only the current account should be used for holding money.

It is not permissible to keep money in a forbidden account and benefit from its returns. If the transactor repents and stops the forbidden investment, and was ignorant of the prohibition at the time of investment, then it is permissible for him to benefit from the forbidden returns. However, if he was aware of the prohibition, he must dispose of the forbidden returns by giving them to the poor and needy. If he does not have sufficient halal money to meet his needs, he is permitted to take from it according to his need, along with repentance and cessation of the forbidden investment.