What is the ruling on money acquired from usury after its owner repents, and what is the method for purifying this money, and is it permissible to work for the father who possesses this money?

If a person involved in usury repents with sincere repentance (tawbah (definition) nasuh), then Allah will accept his repentance. A condition for the repentance of the borrower who dealt with usurious interest is to eliminate the usurious transaction by returning the borrowed money without the interest if the money is still available, or by returning an equivalent amount if it is not. Whatever he bought with this money is lawfully owned by him. He is only required to return the principal amount, as Allah Almighty says: (And if you repent, you will have your principal – [thus] you do no wrong, nor are you wronged). So, if the father returns the principal amount, repents, and shows remorse, then there is nothing against him except to continue in repentance and increase in good deeds. And by extension, there is nothing against his son, the agent.