(27) باب قِتَالِ الْمُسْلِمِ
It was narrated that 'Abdullah said:
"Fighting a believer is Kufr and defaming him is evildoing."
Reference: Sunan an-Nasa'i 4113
In-book reference: Book 37, Hadith 148
English translation: Vol. 5, Book 37, Hadith 4118