Musannaf Ibn Abi Shayba 13:3174

Abu Bakr narrated to us, he said: Ibn ‘Ulayyah narrated to us, from Malik ibn Dinar, he said: A man said to ‘Ata’ ibn Abi Rabah: A man acquired wealth from a forbidden (haram) source. He said: He should return it to its owners. If he does not know its owners, then he should give it away in charity. And I do not know if that will save him from his sin.