If a Jew or a Christian (1) were to transfer to the religion of the Magians, or to any creed outside the faiths of the People of the Book, or if a Magian abandoned his religion for something other than those faiths, he is not allowed to remain upon that new belief. Nothing will be accepted from him except Islam, for every other creed is false, and he has himself acknowledged that falsehood (2). He is therefore treated like an apostate: he is summoned to repent, and if—after being given the opportunity—he still refuses to embrace Islam, the sword is applied and he is put to death, for he has descended to a religion inferior to the one he formerly held.

If someone who is not from the People of the Book—such as an idol-worshipper—embraces Judaism or Christianity, he is permitted to remain upon it, because that religion is higher and more complete than what he previously professed: its followers are legally tolerated, their slaughtered animals are lawful to eat, and intermarriage with them is permissible. The same ruling applies even when the convert was originally a Magian.

Likewise, if an idolater adopts Magianism, he is moving to a creed better than his former one, similar to the case of adopting Judaism.

Anyone whom we have allowed to remain upon a newly adopted Judaism or Christianity has the slaughter of his animals and marriage with him deemed lawful—this is the decisive view adopted in al-Mubdiʿ. Other opinions that contradict this in matters of marriage and slaughter will be cited later.

If a dhimmi lapses into zindīq beliefs, he is not executed, because the jizyah remains due; this is the explicit ruling transmitted by Ibn Hāni (3).

If a Christian rejects Moses, the son of Imran—upon our Prophet and upon him be peace (4)—he thereby leaves Christianity, for by denying Moses he actually belies his own prophet Jesus, who said, “confirming the Torah that came before me” (5); the ruling is the same as if he were to deny Jesus himself.