(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." (JA)
Reference (JA): Sunan Ibn Majah 3941 (JA)
In-book reference (JA): Book 36, Hadith 16 (JA)
English translation (JA): Vol. 5, Book 36, Hadith 3941 (JA)