The Prophet ﷺ said, "There will come a people who hold a covenant of protection. Whoever kills one of them will not smell the fragrance of Paradise, though its fragrance can be detected from a distance of seventy years' travel."
عن النبي ﷺ أنه قال: سيكون قوم لهم عهد، فمن قتل رجلا منهم لم يرح رائحة الجنة، وإن ريحها ليوجد من مسيرة سبعين عاما.
Ahmad (16590) narrated it from Abu Nadr, who said, "Ashjai narrated to us, from Sufyan, from Amash, from Hilal bin Yasaf, from a man," and he related it. Its chain of transmission is sahih.