Musnad Ahmad 285:1

Sufyan ibn 'Uyaynah narrated to us, from Jami' ibn Abi Rashid and 'Asim, from Abu Wa'il, from Qays ibn Abi Gharzah, who said: We used to be called "the brokers" (as-samasirah) during the time of the Messenger of Allah, peace and blessings of Allah be upon him. He came to us at al-Baqi' and said: "O company of merchants"—and he named us with a name better than our name—"selling is attended by oaths and falsehood, so mix it with charity."