The Book Pertaining to the Turmoil and Portents of the Last Hour (Kitab Al-Fitan wa Ashrat As-Sa`ah)

Muslim :: Book 41 : Hadith 6899

Ahnaf b. Qais reported on the authority of Abu Bakra that Allah's Messenger (may peace be upon him) said: When two Muslims confront each other with their swords, both the slayer and the slain are doomed to Hell-Fire.