Tribulations
36/4. Chapter:
Verbally abusing a Muslim is Fusuq (disobedience) and fighting Him is Kufr (ungratefulness to Allah)
Sunan Ibn Majah
حَدَّثَنَا عَلِيُّ بْنُ مُحَمَّدٍ، حَدَّثَنَا وَكِيعٌ، عَنْ شَرِيكٍ، عَنْ أَبِي إِسْحَاقَ، عَنْ مُحَمَّدِ بْنِ سَعْدٍ، عَنْ سَعْدٍ، قَالَ قَالَ رَسُولُ اللَّهِ ـ صلى الله عليه وسلم ـ " سِبَابُ الْمُسْلِمِ فُسُوقٌ وَقِتَالُهُ كُفْرٌ " .
It was narrated from Sa’d that the Messenger of Allah (ﷺ) said: “Verbally abusing a Muslim is Fusuq (disobedience) and fighting him is Kufr.”
Reference : Sunan Ibn Majah 3941In-book reference : Book 36, Hadith 16English translation : Vol. 5, Book 36, Hadith 3941