Sheikh ibn Uthaimeen (May Allah have mercy on him) relates that the conclusion to what majority of the scholars have said is that ‘whoever follows the religion of the people of the book, embraces their doctrines, even though he believes in the trinity, then his sacrifice is permissible and his marriage is permissible’.  

The marriage to a Jewish, or a Christian woman has been allowed for necessity, and is not the basis for the building a Muslim family. A permissible matter may become forbidden if it results in harm and consequences which threaten the Muslim communities’ present and future. For this reason, a lot of scholars have forbidden the marriage to the women of the people of the book now. This is because no matter how sincere she is to her husband, she will not forget her beliefs that she was raised upon, or her nationality to which she belongs, nor her language that she learnt since he was a child. Many incidents confirm this, in addition to the fact that the marriage to the women of the book, is harmful to Muslim women. 

It has come in a narration that Umar bin Al Khattab prevented one of the governors from marrying a Jewish woman. When the governor asked him whether she was forbidden or permissible, Umar said to him: “And who is for the believing women?” meaning that if a muslim man married a woman from the women of the book, then he has made the marriage of a muslim woman difficult, because a muslim woman can only marry a muslim man.