Musannaf Ibn Abi Shayba 13:2528

Abu Bakr narrated to us, he said: Ibn Abi Za’idah narrated to us, from Muhammad ibn ‘Amr, from Abu Salamah, from Abu Sa’id, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "A dirham is not valid for two dirhams, nor a sa’ for two sa’s. The dinar for the dinar, and the dirham for the dirham."