Sahih Muslim 4379
صحيح مسلم#4379SahihAbdullah (b. Mas'ud) reported:Allah's Apostle (ﷺ) having said: No person who is killed unjustly, but the share of (this offence of his also) falls upon the first son of Adam, for he was the first to introduce killing
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Every narration in Sahih Muslim is accepted as Sahih (authentic) by the established status of the book.
In-book reference: 28:38