(202) بَابُ سِبَابِ الْمُسْلِمِ فُسُوقٌ
'Abdullah reported that the Prophet, may Allah bless him and granthim peace, said, "Reviling a Muslim is deviant behaviour and killing himis disbelief." (ID)
Reference (ID): Al-Adab Al-Mufrad 431 (ID)
In-book reference (ID): Book 24, Hadith 13 (ID)
English translation (ID): Book 24, Hadith 431 (ID)