He has become Muslim but his wife has not, and she is not from among the People of the Book. Is it permissible for him to live with her?
Question

                Is the major sin of zinaa committed, if a married man becomes Muslim, but his wife doesn't become Muslim, and is not a christian or jew, and they continue to have sexual realtions, or if a married woman becomes Muslim, and her husband does not become Muslim, and they continue to have sexual relations?  Jazak-Allah Khairan.
Praise be to Allah.It 
          is not permissible for a Muslim to remain in a marital relationship 
          with a wife who is not Muslim, because Allaah says (interpretation of 
          the meaning): 
“And 
          do not marry Al-Mushrikaat (idolatresses) till they believe (worship 
          Allaah Alone) [al-Baqarah 2:221] 
“Likewise 
          hold not the disbelieving women as wives” [al-Mumtahanah 60:10] 
“They 
          are not lawful (wives) for the disbelievers nor are the disbelievers 
          lawful (husbands) for them” [al-Mumtahanah 60:10] 
‘Umar 
          (may Allaah be pleased with him) divorced two of his wives who were 
          mushriks when this aayah was revealed. Ibn Qudaamah stated in al-Mughni 
          that there is ijmaa’ (scholarly consensus) on this point. He 
          said, “There is no difference of opinion among the scholars that their 
          women are forbidden (for marriage).” (al-Mughni 7/503)   
          
Allaah 
          has made an exception in the case of women from among the People of 
          the Book [Jews and Christians]. He says (interpretation of the meaning): 
          
“(Lawful to you in marriage) are chaste women 
          from the believers and chaste women from those who were given the Scripture 
          (Jews and Christians) before your time” [al-Maaa’idah 
          5:5] 
The 
          word “chaste” (muhsanaat) means that they do not engage in zinaa 
          (unlawful sexual relationships).   
As 
          the wife mentioned in the question is not from among the People of the 
          Book, her Muslim husband has to fear Allaah and leave her, because his 
          relationship with her is haraam according to sharee’ah, and persisting 
          in it is zinaa and is haraam. If a woman becomes Muslim and her husband 
          is a kaafir, whether he is from among the People of the Book or not, 
          the marriage contract immediately becomes null and void, because of 
          the evidence cited above. She becomes forbidden to him by virtue of 
          her becoming Muslim, and she is no longer permissible for him, unless 
          he becomes Muslim during her ‘iddah (waiting period following divorce). 
          And Allaah knows best.  
See 
          a similar question in Fataawa Islaamiyyah, compiled by Muhammad al-Musnad, 
          3/229.