This is another article in the chapter Justice from the classical manual on Sharia called Reliance of the Traveller. The articles are posted one by one in the order they are given in the book.
08.0 APOSTASY FROM ISLAM (RIDDA)
(0: Leaving Islam is the ugliest form of unbelief (kufr) and the worst. It may come about through sarcasm, as when someone is told, “Trim your nails, it is sunna,” and he replies, “I would not do it even if it were,” as opposed to when some circumstance exists which exonerates him of having committed apostasy, such as when his tongue runs away with him, or when he is quoting someone, or says it out of fear.)
08.1 When a person who has reached puberty and is sane voluntarily apostatizes from Islam, he deserves to be killed.
08.2 In such a case, it is obligatory for the caliph (A: or his representative) to ask him to repent and return to Islam. If he does, it is accepted from him, but if he refuses, he is immediately killed.
08.3 If he is a freeman, no one besides the caliph or his representative may kill him. If someone else kills him, the killer is disciplined (def: (17) (0: for arrogating the caliph’s prerogative and encroaching upon his rights, as this is one of his duties).
08.4 There is no indemnity for killing an apostate (0: or any expiation, since it is killing someone who deserves to die).
08.5 If he apostatizes from Islam and returns several times, it (0: i.e. his return to Islam, which occurs when he states the two Testifications of Faith (def: 08.7(12))) is accepted from him, though he is disciplined (017).
08.6 (A: If a spouse in a consummated marriage apostatizes from Islam, the couple are separated for a waiting period consisting of three intervals between menstruations. If the spouse returns to Islam before the waiting period ends, the marriage is not annulled but is considered to have continued the whole time (dis: m7.4).)