The Messenger of Allah ﷺ said, "No soul is killed unjustly without the first son of Adam bearing a share of the guilt for its blood, because he was the first to establish the practice of killing."
قال رسول الله ﷺ: لا تقتل نفس ظلما، إلا كان على ابن آدم الأول كفل من دمها، لانه كان أول من سن القتل.
Bukhari narrated it in the Book of Blood Money (6867), and Muslim narrated it in the Book of Qasama (167:27) both through the route of Amash, from Abdullah bin Mura, from Masruq, from Abdullah, who said, and then he mentioned it.