— Muhammad Arabian religious leader and the founder of Islam 570 - 632
it is true about one of them."
Muwatta of Imam Malik, Speech, hadith 1 http://ahadith.co.uk/permalink-hadith-4899
Variante: Malik related to me from 'Abdullah ibn Dinar from 'Abdullah ibn 'Umar that the Messenger of Allah, may Allah bless him and grant him peace, said, "If a man says to his Muslim brother, 'O unbeliever!' it is true about one of them."