Arabic (Original)
حَدَّثَنَا عَبْد اللَّهِ قَالَ وَجَدْتُ فِي كِتَابِ أَبِي حَدَّثَنَا حَجَّاجٌ أَخْبَرَنَا شُعْبَةُ عَنْ عَبْدِ اللَّهِ بْنِ دِينَارٍ عَنِ ابْنِ عُمَرَ عَنْ النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ أَنَّهُ قَالَ إِذَا قَالَ الرَّجُلُ لِأَخِيهِ أَنْتَ كَافِرٌ أَوْ يَا كَافِرُ فَقَدْ بَاءَ بِهَا أَحَدُهُمَا.
English Translation
Abdullah said: I found in my father's book: Hajjaj told us, Shu'bah informed us, from Abdullah ibn Dinar, from Ibn Umar, from the Prophet, peace and blessings be upon him, that he said, "If a man says to his brother, 'You are a disbeliever,' or 'O disbeliever,' then it returns to one of them."