The Prophet ﷺ said, "Whoever kills a person under a covenant of protection will not smell the fragrance of Paradise, though its fragrance can be detected from a distance of forty years' travel."
عن النبي ﷺ قال: من قتل نفسا معاهدا لم يرح رائحة الجنة، وإن ريحها ليوجد من مسيرة أربعين عاما.
Bukhari (6914) narrated it from Qays bin Hafs, who said, Abdul-Wahid narrated to us, who said, Hasan narrated to us, who said, Mujahid narrated to us, from Abdullah bin Amr, and he mentioned it.