The Messenger of Allah ﷺ said, "No soul is killed unjustly except that a share of its blood falls upon the first son of Adam, 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، لأنه كان أول من سن القتل.
Bukhari narrated it in the Book of Itisam (7321), and Muslim in the Book of Qasama (1677), both through the route of Amash, from Abdullah bin Mura, from Masruq, from Abdullah, and he mentioned it.