Narrated by Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: The blood of a Muslim who testifies that Allah alone is the true deity and that I am the Messenger of Allah is not lawful, except in three cases: (1) a married adulterer, (2) one who is killed in retaliation for murder, and (3) one who leaves the religion and separates from the community.