Authentic. Al-Bukhārī (2/294, 4/326), al-Nasā’ī (2/242), and Ibn Mājah (2686) narrated it from ʿAbd Allāh ibn ʿAmr, from the Prophet (peace and blessings be upon him), with this wording. Al-Nasā’ī’s wording is: “Whoever kills someone from among the people under covenant...” Ahmad likewise narrated it (2/186), and al-Hākim (2/126–127) graded it authentic according to the criteria of the two Shaykhs; al-Dhahabī concurred.
450—(According to another version: “Whoever kills a man from among the people under covenant will not smell the fragrance of Paradise.” Al-Nasā’ī.) p. 317.
Authentic. Al-Nasā’ī (2/242) narrated it through al-Qāsim ibn Mukhaymirah, from a man among the Companions of the Prophet (peace and blessings be upon him), who reported that the Messenger of Allah (peace and blessings be upon him) said it, with the addition: “Its fragrance can indeed be detected from a distance of seventy years’ travel.” Ahmad also narrated it (4/237, 5/369), and its chain is authentic. The anonymity of a Companion does not undermine a report according to Ahl al-Sunnah, as established in the appropriate section of hadith terminology.
It also has supporting evidence in a hadith traced back to the Prophet from Abū Hurayrah, with the wording: “Indeed, whoever kills a person under covenant who enjoys the covenant of Allah and the covenant of His Messenger has violated Allah’s covenant. He will not smell the fragrance of Paradise, even though its fragrance can be detected from a distance of seventy years’ travel.” Al-Hākim (2/127) narrated it through Maʿdī ibn Sulaymān, who said: Ibn ʿAjlān narrated to us from his father, from Abū Hurayrah. Al-Hākim said: “It is authentic according to Muslim’s criteria”! Al-Dhahabī concurred! Yet Muslim did not narrate from Maʿdī, and he is moreover weak, as the hadith master stated in al-Taqrīb.
451—(He (peace be upon him) said: “The blood of a Muslim is not lawful except in one of three cases: a life for a life, a previously married adulterer, and one who abandons his religion and separates from the community.” Narrated by al-Bukhārī and Muslim.) p. 318.