The Messenger of Allah ﷺ said, "Whoever kills a person under covenant without just cause, Allah will forbid Paradise to him."
قال رسول الله ﷺ: من قتل معاهدا في غير كنهه حرم الله عليه الجنة.
Reported by Abu Dawud (2760), Nasai (4747), and Ahmad (20377), and Hakim declared it sahih (2/142) as did Bayhaqi (9/231), all of them through routes from Uyayna bin Abdul-Rahman, from his father, from Abu Bakra, who related it.Its chain is hasan because of Uyayna bin Abdul-Rahman bin Jawshan Ghatafani, whose hadith is hasan. Ibn Main and Ahmad said of him, "There is no harm in him," and Nasai said, "Trustworthy."The hadith has other chains besides this one, but what I have mentioned here is the most sahih of them. His saying, "in other than its rightful place," means "not as it deserves."