Shaykh al-Islam (Ibn Taymiyah) said in his discussion of the extreme views of the Raafidis and of the Nusayris and Ismailis concerning ‘Ali, that all of these kuffaar are worse kaafirs than the Jews and Christians. If one of them does not make an open display of that, then he is one of the munaafiqeen (hypocrites) who will be in the lowest level of Hell, and those who do make an open display of that are the worst of the kaafirs in kufr. And he said: it is not permitted to marry their women, because they are apostates and are the worst kind of apostates.
Concerning the Nusayris he said: the scholars are agreed that it is not permitted to intermarry with them, or for a man to marry his female relative to one of them, or to marry one of their women.
Mutawaatir reports from the righteous salaf indicate that it is forbidden for a Muslim woman from among Ahl al-Sunnah to marry someone from among the followers of bid’ah who has been judged to be a kaafir, and that this type of marriage is null and void.
See Mawqif Ahl al-Sunnah wa’l-Jamaa’ah min Ahl al-Ahwaa ‘wa’l-Bida’ by Dr. Ibraaheem al-Raheeli, 1/377-380
