(4) باب سِبَابُ الْمُسْلِمِ فُسُوقٌ وَقِتَالُهُ كُفْرٌ
It was narrated from Ibn Mas'ud that the Messenger of Allah (ﷺ)said:
"Verbally abusing a Muslim is Fusuq disobedience and fightinghim is Kufr (ungratefulness to Allah).'" (JA)
Reference (JA): Sunan Ibn Majah 3939 (JA)
In-book reference (JA): Book 36, Hadith 14 (JA)
English translation (JA): Vol. 5, Book 36, Hadith 3939 (JA)