Sunan an-Nasa'i #4112 · The Book of Fighting [The Prohibition of Bloodshed]

Sunan an-Nasa'iIt was narrated that Abu Wa'il said
Sunan an-Nasa'i · Book 37 · The Book of Fighting [The Prohibition of Bloodshed]
Sunan an-Nasa'i · كتاب 37 · كتاب القتال [تحريم سفك الدماء]
"'Abdullah said: 'Defaming a Muslim is evildoing and fighting him is Kufr
أَخْبَرَنَا قُتَيْبَةُ بْنُ سَعِيدٍ، قَالَ حَدَّثَنَا جَرِيرٌ، عَنْ مَنْصُورٍ، عَنْ أَبِي وَائِلٍ، قَالَ قَالَ عَبْدُ اللَّهِ سِبَابُ الْمُسْلِمِ فُسُوقٌ وَقِتَالُهُ كُفْرٌ ‏.‏
Reference : Sunan an-Nasa'i 4112In-book reference : Book 37, Hadith 147