Musnad Ahmad 285:4

Bahz narrated to us, he said: Shu'bah narrated to us, he said: Habib ibn Abi Thabit informed me, he said: I heard Abu Wa'il narrating from Qays ibn Abi Gharzah, he said: The Messenger of Allah (peace and blessings of Allah be upon him) came out to us while we were selling merchandise, and we were called brokers. He said: "O assembly of merchants, this selling of yours is intermixed with idle talk or swearing, so mix it with charity, or with something of charity."