It is narrated from Sayyiduna Abdullah (bin Mas'ud) رضي الله عنه that the Messenger of Allah صلى الله عليه وسلم said: "The blood of a Muslim man who testifies that 'There is no god but Allah' (i.e., the Oneness of Allah) and my Messengership is not lawful except for one of three reasons: (1) life for life, (2) a married adulterer, (3) one who leaves the religion of Islam and separates from the community."