"The Messenger of Allah said: 'Defaming a Muslim is evildoing and fighting him is Kufr.'" I said to Abu Wa'il: "Did you hear it from 'Abdullah?" He said: "Yes."
Sunan an-Nasa'i Book 37, Hadith 145
← Previous Hadith "I said to Hammad: 'I heard Mansur, and Sulaiman, and Zubaid narrating from Abu Wa'il, from 'Abdullah, that the Messenger of Allah said: "Defaming a Muslim is evildoing and fighting him is Kufr." - Who are you worried about? Are you worried about Mansur? Are you worried about Zubaid? Are you worried about Sulaiman?' He said: 'No, but I am worried about Abu Wa'il.'"

Sunan an-Nasa'i Book 37, Hadith 144 Next Hadith → "The Messenger of Allah said: 'Defaming a Muslim is evildoing and fighting him is Kufr.'"

Sunan an-Nasa'i Book 37, Hadith 146