What should one do whose legitimate money has become mixed with suspicious money?

If the permissibility of a portion of wealth is uncertain, but its unlawfulness is not clear, there is no harm in utilizing it, though it is disliked. It is more cautious to dispose of it if its exact nature or amount is known. Otherwise, one should give away what is most likely its equivalent, based on the Prophet's (peace be upon him) saying: "Leave that which makes you doubt for that which does not make you doubt."