Trials and Fierce Battles (Kitab Al-Fitan Wa Al-Malahim)
Dawud :: Book 35 : Hadith 4259
Narrated Zayd ibn Thabit:
The verse "If a man kills a believer intentionally, his recompense is Hell to abide therein for ever" was revealed six months after the verse "And those who invoke not with Allah any other god, nor slay such life as Allah has made sacred, except for just cause in Surat al-Furqan.