"The Messenger of Allah [SAW] said: 'Defaming a Muslim is evildoing and fighting him is Kufr.'" I said to Abu Wa'il: "Did you hear it from 'Abdullah?" He said: "Yes." (Using translation from Nasāʾī 4110)

قَالَ رَسُولُ اللهِ ﷺ «سِبَابُ الْمُسْلِمِ فُسُوقٌ وَقِتَالُهُ كُفْرٌ» قُلْتُ لِأَبِي وَائِلٍ أَنْتَ سَمِعْتَهُ مِنْ عَبْدِ اللهِ؟ قَالَ نَعَمْ