Sunan An-Nasa'i

It was narrated that Abu Bakrah said:""I heard the Messenger of Allah [SAW] say: 'If two Muslims confront each other with their swords and one of them kills the other, both the killer and the slain will be in Hell.'"" They said: ""O Messenger of Allah, (we understand about) the killer, but what about the one who is killed?"" He said: ""He wanted to kill his companion