Musannaf Ibn Abi Shayba 13:2951

Abu Bakr narrated to us, he said: Waki’ narrated to us, he said: Al-Rabi’ narrated to us, he said: I said to Al-Hasan, "O Abu Sa’id, I have debased dirhams (coins of low value) gathered with me, so I sell them and clarify their condition." He said: "There is no harm in it."