NASAI 4105:
from ʿAbdullāh —
"Defaming a Muslim is evildoing and fighting him is Kufr." (Sahih Mawquf)
النسائي ٤١٠٥:
عن عبد الله —
سِبَابُ الْمُسْلِمِ فُسُوقٌ وَقِتَالُهُ كُفْرٌ