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 ‏"‏ ‏.‏

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