The Prophet ﷺ said, "Whoever kills a person under a covenant of protection from Allah and His Messenger has violated the covenant of Allah. He shall not smell the fragrance of Paradise, though its fragrance can be detected from a distance of seventy years' travel."
عن النبي ﷺ قال: ألا من قتل نفسا معاهدا له ذمة الله وذمة رسوله، فقد أخفر بذمة الله، فلا يرح رائحة الجنة، وإن ريحها ليوجد من مسيرة سبعين خريفا.
Tirmidhi (1403) and Ibn Majah (2687) both narrated it from Muhammad bin Bashshar, who said, Madi bin Sulayman, who is al-Basri, narrated to us, who said, Ibn Ajlan informed us, from his father, from Abu Hurairah, and he related it.Tirmidhi said, "This is a hasan sahih hadith, and it has been narrated through other routes from Abu Hurairah, from the Prophet ﷺ."I say, its chain is hasan because of Muhammad bin Ajlan, for his hadith is hasan.