Is money returned from a person who trades in music tapes and films containing indecent scenes considered doubtful money?

This question has two possibilities:

The first: That giving the money was a loan. In this case, your money is lawful, but it is not permissible to lend it to someone who will use it for trade in haram (unlawful) things.

The second: That giving the money was a Mudarabah (a form of partnership where one party provides the capital and the other provides labor) and an investment. In this case, no part of the profit is lawful for you if its source was unlawful trade. As for the principal capital, it is lawful for you, and you must repent if you knew about the unlawful source of his trade.