´It was narrated from 'Abdur-Rahman bin 'Abdullah, from his father, that:` The Messenger of Allah [SAW] said: "Defaming a Muslim is evildoing and fighting him is Kufr."
Hadith ReferenceSunan an-Nasa'i / The Book Of Fighting (The Prohibition Of Bloodshed) / Hadith: 4113
Hadith Gradingالألبانی:صحيح الإسناد | زبیر علی زئی:صحيح