Musnad Ahmad 1007:29

Ya'qub narrated to us, my father narrated to us, from Ibn Ishaq, Ma'bad ibn Ka'b ibn Malik narrated to me, that he heard Abu Qatadah al-Sulami narrating that he 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."