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 معاهدا لم يرح رائحة الجنة، وإن ريحها توجد من مسيرة أربعين عاما.
Bukhari narrated it in the Book of Jizya and Truces (3166), from Qays bin Hafs, who said, Abdul-Wahid narrated to us, who said, Hasan bin Amr narrated to us, who said, Mujahid narrated to me, from Abdullah bin Amr, and he mentioned it.