Musnad Ahmad 26:573

Waki’ narrated to us, Sufyan narrated to us, from al-A’mash, from ‘Abdullah ibn Murrah, from Masruq, from ‘Abdullah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "There is no soul that is killed unjustly, except that the first son of Adam bears a portion of its blood, because he was the first to establish the practice of killing."