Arabic (Original)
حَدَّثَنَا يَعْلَى بْنُ عُبَيْدٍ حَدَّثَنَا فُضَيْلٌ يَعْنِي ابْنَ غَزْوَانَ عَنْ نَافِعٍ عَنِ ابْنِ عُمَرَ قَالَ قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ أَيُّمَا رَجُلٍ كَفَّرَ رَجُلًا فَإِنْ كَانَ كَمَا قَالَ وَإِلَّا فَقَدْ بَاءَ بِالْكُفْرِ.
English Translation
Ya'la ibn 'Ubayd narrated to us: Fudayl, that is Ibn Ghazwan, narrated to us, from Nafi', from Ibn 'Umar, who said: The Messenger of Allah, peace and blessings be upon him, said: "Whatever man declares another man a disbeliever — if he is indeed as he said, well and good; otherwise it returns upon himself as disbelief."