What evidence is there that a Muslim man can not marry a chaste woman of the book if she is an ex-Muslim?

Qur'an 5:5 permits Muslim men to marry chaste women of the book. However, according to IslamWeb, there is an exception: a Muslim man may not marry a woman who is an ex-Muslim (a.k.a., an apostate). They quote: > Ibn Qudaamah said: “It is prohibited to marry an apostate woman, no matter what religion she adopts; because it is not proved for her the ruling of the people of the religion to which she converted by one's approval of her doing so. Based on this, it is not lawful for him to marry her with greater reason.” [Al-Mughni 7/131] > IslamWeb The English in this translation is not clear, so I'm not sure what "it is not proved for her the ruling of the people of the religion to which she converted by one's approval of her doing so" actually means. This leads me to my question: **Question**: What evidence is there that a Muslim man can not marry a chaste woman of the book if she is an ex-Muslim? I think IslamWeb refers to Ibn Qudamah on Wikipedia, who was around hundreds of years after the Prophet. If this is correct, what IslamWeb presents is just one scholar's opinion. However, it's possible this scholar had other justifications for making this ruling.