´It was narrated from 'Abdullah that the Messenger of Allah said:` "It is not permissible to shed the blood of a Muslim except in one of three cases: A soul for a soul, a adulterer who has been married, and one who separates leaving his religion."
Hadith ReferenceSunan an-Nasa'i / The Book of Oaths (qasamah), Retaliation and Blood Money / Hadith: 4725