Musnad Abu Ya'la al-Mawsili 152:301

Abu Khaythama narrated to us, Muhammad ibn Sabiq narrated to us, Isra'il narrated to us, from al-A'mash, from Ibrahim, from Alqama, from Abdullah, who said: The Messenger of Allah (may Allah bless him and grant him peace) said: "The believer is not one who frequently curses, nor one who frequently defames, nor one who is obscene, nor one who is foul-mouthed."