Musannaf Ibn Abi Shayba 13:2298

Abu Muhammad Abdullah ibn Yunus narrated to us, he said: Abu Abd al-Rahman Baqi ibn Makhlad narrated to us, he said: Abu Bakr narrated to us, he said: Waki' narrated to us, he said: Sufyan narrated to us, from Uthman ibn al-Aswad, from Mujahid, regarding a man who exchanges a dinar with a man, and a qirat of gold remains over: He said: There is no harm in him taking for it such and such amount of dirhams.