Musnad Ahmad Hadith 19590

Khwaja Hasan (may Allah have mercy on him) says that Abu Musa (may Allah be pleased with him) had a brother who actively participated in acts of discord. He would forbid him, but he would not desist. He said to him, "If I thought that even a little advice would be enough for you, which in my opinion is less than this (I would still advise you)." And the Noble Prophet (ﷺ) said: "When two Muslims come face to face with swords and one of them kills the other, both the killer and the killed will go to Hell." Someone asked, "O Messenger of Allah (ﷺ)! The matter of the killer is understandable, but what about the killed one?" The Noble Prophet (ﷺ) said, "He also wanted to kill his companion."