Hadith 56:1
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 kafir!' it is true about one of them."
حَدَّثَنِي مَالِكٌ، عَنْ عَبْدِ اللَّهِ بْنِ دِينَارٍ، عَنْ عَبْدِ اللَّهِ بْنِ عُمَرَ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ " مَنْ قَالَ لأَخِيهِ يَا كَافِرُ . فَقَدْ بَاءَ بِهَا أَحَدُهُمَا "