The Shaikh, the Imam, the Marja`, the `Alim, Al-`Allamah Mustafa as-Suyuti ar-Ruhaibani mentioned about the marriage in question and any marriage like it:
If one of the married couple that is not a Jew or Christian becomes a Muslim or if an unbelieving woman becomes a Muslim while married to an unbelieving man and they have had sexual intercourse, then the marriage ends after one monthly cycle (Ar. `iddah).
This is due to what has been narrated by Imam Malik ibn Anas in his Muwatta’ from Ibn Shihab who said, “The time between Safwan ibn Umayyah becoming Muslim and his wife – who was the daughter of Al-Walid ibn al-Mughirah was one month.
His wife had become Muslim on the day of the Conquest of Makkah and Safwan remained with her up until he was in the battle of Hunain and At-Ta’if – while at that time he was an unbeliever – then he became Muslim after that.
After that point, the Prophet, peace and blessings of Allah be upon him, did not separate them and dissolve their marriage but he upheld the marriage of his wife. This was one month.”
Ibn `Abdul Barr has also mentioned, “This hadith is very famous and is stronger and more well known than its’ chain of transmission.”
Ibn Shabramah has said, “The people – in the time of the Messenger of Allah, peace and blessings of Allah be upon him – when the man would become Muslim before the wife or the wife before the husband, then whoever should become Muslim before the end of the monthly cycle, the woman will remain his wife.
If he should become Muslim after that point, then there is no marriage between them and a new covenant of marriage will have to be ratified.”
If one of the married couple should become a Muslim during the monthly cycle and before its’ completion, then the marriage stands as valid between the two as previously mentioned.
If this does not come to pass, then the marriage dissolves at the end of the monthly cycle from the time that the first one become Muslim, whether it be the husband or the wife.
The woman has the right of maintenance during this time if she became Muslim before him and he does not become a Muslim.
If they both become unbelievers – meaning that they both apostate from Islam – or one of them apostates after having sexual intercourse in the marriage, then they are to wait one monthly cycle. This is just the same as the case if one of them became a Muslim.
If one of them or they both repent from their apostasy before the end of the monthly cycle, then they are held as still being married with their current contract.
If it cannot be determined or is not clear when this happened, then the marriage dissolves from the time that the apostasy happened. If they apostate or one of them apostates before sexual intercourse of the valid marriage, then the marriage is nullified due to their being two different religions, namely that one is a Muslim and the other an apostate.
Taken from Matalib Uwli in-Nuha fi Sharhi Ghayat il-Muntaha, vol.1, pp. 272-273
Taken from the meeraath website