Musnad Ahmad 1007:28

Yazid ibn Harun narrated to us, Muhammad ibn Ishaq informed us, from Ma'bad ibn Ka'b ibn Malik, from Abu Qatadah, who said: I heard the Messenger of Allah, peace and blessings of Allah be upon him, saying: "Beware of frequent swearing in selling; for it promotes the commodity, then it wipes out the blessing."