1445 - Abu 'Abd Allah narrated to us, he said: Muhammad ibn Ja'far narrated to us, he said: Shu'bah narrated to us, from Zubayd al-Yamami, he said: I heard Abu Wa'il narrate from 'Abd Allah, from the Prophet (may Allah bless him and grant him peace) that he said: "Reviling a Muslim is an act of immorality (fusuq), and fighting him is an act of disbelief (kufr)."