حَدَّثَنَا سُلَيْمَانُ بْنُ حَرْبٍ، قَالَ: حَدَّثَنَا شُعْبَةُ، عَنْ زُبَيْدٍ قَالَ: سَمِعْتُ أَبَا وَائِلٍ، عَنْ عَبْدِ اللهِ، عَنِ النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: ”سِبَابُ الْمُسْلِمِ فُسُوقٌ، وَقِتَالُهُ كُفْرٌ.“
It is narrated from Sayyiduna Abdullah (may Allah be pleased with him) that it is reported from the Prophet (peace and blessings of Allah be upon him): "Abusing a Muslim is a sin, and fighting him is disbelief."