The difference between a Jewish or Christian wife and a wife who does not pray
Question

                I read a fatwa which you issued to a Muslim man whose Muslim wife does not pray, and you told him that he had to divorce her. I know that it is permissible for a Muslim man to have a Jewish or Christian wife, and Jewish and Christian women do not pray. Is there some mistake?.
Praise be to Allah.There is no 
    mistake in the fatwa referred to. Rather the mistake comes from the 
    questioner wanting to regard as equal a woman who is supposedly Muslim but 
    does not pray and a woman who is Jewish or Christian, on the basis that 
    neither of them prays. 
This 
    regarding them as equal is not valid, because there is a difference between 
    them, which is that not praying is major kufr and apostasy that puts a 
    person beyond the pale of Islam. This has been explained in many answers on 
    this site, such as the answers to questions no. 
    9400 and 
    5208. 
Based on 
    this, the woman who does not pray is a kaafir and an apostate from Islam. 
The ruling 
    on one who has apostatized from Islam is more severe than the ruling on a 
    Jew or Christian. 
Shaykh 
    al-Islam Ibn Taymiyah said: 
The apostate 
    is worse than a kaafir in many ways. End quote. 
Majmoo’ 
    al-Fataawa, 2/193 
Hence meat 
    slaughtered by an apostate cannot be eaten, whereas meat slaughtered by a 
    Jew or Christian may be eaten. It is not permissible for a Muslim to marry 
    an apostate woman, and if his wife apostatizes, the marriage contract 
    becomes null and void, but it is permissible for a Muslim to marry a Jewish 
    or Christian woman. 
The crux of 
    the matter is the ruling that one who does not pray is a kaafir. Those who 
    are of this view forbade marriage to a woman who does not pray, and said 
    that it is obligatory to leave a woman if she stops praying. This is the 
    view of Imam Ahmad (may Allaah have mercy on him) and was stated in fatwas 
    by a number of scholars, such as Shaykh Ibn Baaz (may Allaah have mercy on 
    him), Shaykh Ibn ‘Uthaymeen (may Allaah have mercy on him) and Shaykh Saalih 
    al-Fawzaan (may Allaah preserve him). Our fatwa on this issue and similar 
    issues is based on their fatwas.  
Similarly, 
    if a woman does something that implies kufr, such as vilifying Allaah, may 
    He be exalted, or vilifying His Messenger  (peace and blessings of 
    Allaah be upon him), and she persists in her kufr and does not repent, then 
    it is not permissible for her to remain the wife of a Muslim. The same 
    applies if a husband is ruled to be an apostate, then he and his wife must 
    be separated. 
And Allaah 
    knows best.