Reviling religion is apostasy from Islam. The same applies to reviling the Qur’aan or the Messenger (blessings and peace of Allah be upon him): it is apostasy from Islam, and kufr (disbelief) after faith - we seek refuge with Allah. But it does not mean that the wife is divorced (talaaq); rather they should be separated without divorce. It cannot be divorce; rather she becomes haraam for him because she is a Muslim woman whereas he is a kaafir, and she remains haraam for him until he repents. If he repents and her ‘iddah has not yet ended, she goes back to him without any need for anything, i.e., if he repents and turns back to Allah, she goes back to him. But if her ‘iddah has ended and he has not repented, then she may marry whomever she wants. That is like a divorce but it is not a divorce (talaaq); rather it is like divorce because Allah has forbidden Muslim women for kaafir men.
If he repents after the ‘iddah has ended and he wants to (re)marry her, there is nothing wrong with that, but it should be done with a new marriage contract, so as to be on the safe side and avoid an area concerning which the scholars differed. Some scholars think that she is permissible for him without a new marriage contract: if she chose him and did not marry anyone else after the ‘iddah ended, she remains as she was (i.e., still married). However, the majority say that when the ‘iddah ends, she becomes irrevocably divorced from him and becomes a non-mahram to him, and she cannot become permissible for him except with a new marriage contract. So it is better and more on the safe side to do a new marriage contract. This applies if the ‘iddah ended before he repented. But if he repents before the ‘iddah ends, then she is still his wife, because the Prophet (blessings and peace of Allah be upon him) accepted the marriage contracts of men who became Muslim after their wives did, before the wives’ ‘iddahs ended. End quote.
Shaykh ‘Abd al-‘Azeez ibn Baaz (may Allah have mercy on him)