Musnad Ahmad 657:1

Waki’ narrated to us, Al-A’mash narrated to us, from Abu Wa’il, from Qays ibn Abi Gharzah, who said: We used to buy loads [of produce] in Medina, and we used to call ourselves "the brokers." The Messenger of Allah (peace and blessings of Allah be upon him) came to us and gave us a name that was better than what we called ourselves. He said: "O company of merchants, this selling is attended by idle talk and swearing, so mix it with charity."