It is unlawful to shed the blood of a Muslim who testifies that there is no god but Allah and that Muhammad is the Messenger of Allah

It is unlawful to shed the blood of a Muslim who testifies that there is no god but Allah and that Muhammad is the Messenger of Allah, except in one of three cases: a married person who commits adultery, they are to be stoned; one who goes forth to fight against Allah and His Messenger, they are to be killed, crucified, or exiled from the land; or one who commits murder, for which he is killed in retribution. [An-Nasaa’i]