I went to help that man (i.e., `Ali), and on the way I met Abu Bakra who asked me, "Where are you
going?" I replied, "I am going to help that man." He said, "Go back, for I heard Allah's Messenger (ﷺ)
saying, 'If two Muslims meet each other with their swords then (both) the killer and the killed one are
in the (Hell) Fire.' I said, 'O Allah's Messenger (ﷺ)! It is alright for the killer, but what about the killed one?'
He said, 'The killed one was eager to kill his opponent."
Sahih al-Bukhari Book 87, Hadith 14