He was asked:

What should a man do when his lawful wealth becomes mixed with unlawful wealth?

He replied:

He must weigh out the unlawful portion and return it to its owner. The lawful portion belongs to him. If he does not know the owner and cannot ascertain his identity, he should give it in charity on his behalf.

He—may Allah have mercy on him—was asked:

A woman used to be a singer and, in her ignorance, amassed considerable wealth. She has since repented, performed Hajj to the House of Allah Most High, and remained steadfast in obeying Allah. If she uses the wealth she acquired, whether lawfully or otherwise, for food and charity, will she be rewarded for doing so?

He replied:

If the money is earned in exchange for an item or service that is lawful in itself, but becomes unlawful because of the intended purpose—for example, selling grapes to someone who will make wine from them, or being hired to press grapes for wine or to transport wine—then the person does this in return for payment, but it is not lawful for him to consume that payment.