Musnad Abu Ya'la al-Mawsili 153:148

Muhammad ibn Bashar narrated to us, Abu 'Amir narrated to us, Kathir ibn Zayd al-Madani narrated to us, he said: I heard Salim ibn 'Abdullah narrating from his father, he said: The Messenger of Allah (may Allah bless him and grant him peace) said: "The believer is not one who frequently curses."