(4) باب 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 fightinghimis Kufr." (ES)
Reference (ES): Sunan Ibn Majah 3941 (ES)
In-book reference (ES): Book 36, Hadith 16 (ES)
English translation (ES): Vol. 5, Book 36, Hadith 3941 (ES)