Revertion to Islam by either the husband or the wife

يَٰٓأَيُّهَا ٱلَّذِينَ ءَامَنُوٓا۟ إِذَا جَآءَكُمُ ٱلْمُؤْمِنَٰتُ مُهَٰجِرَٰتٍۢ فَٱمْتَحِنُوهُنَّ ۖ ٱللَّهُ أَعْلَمُ بِإِيمَٰنِهِنَّ ۖ فَإِنْ عَلِمْتُمُوهُنَّ مُؤْمِنَٰتٍۢ فَلَا تَرْجِعُوهُنَّ إِلَى ٱلْكُفَّارِ ۖ لَا هُنَّ حِلٌّۭ لَّهُمْ وَلَا هُمْ يَحِلُّونَ لَهُنَّ ۖ وَءَاتُوهُم مَّآ أَنفَقُوا۟ ۚ وَلَا جُنَاحَ عَلَيْكُمْ أَن تَنكِحُوهُنَّ إِذَآ ءَاتَيْتُمُوهُنَّ أُجُورَهُنَّ ۚ وَلَا تُمْسِكُوا۟ بِعِصَمِ ٱلْكَوَافِرِ وَسْـَٔلُوا۟ مَآ أَنفَقْتُمْ وَلْيَسْـَٔلُوا۟ مَآ أَنفَقُوا۟ ۚ ذَٰلِكُمْ حُكْمُ ٱللَّهِ ۖ يَحْكُمُ بَيْنَكُمْ ۚ وَٱللَّهُ عَلِيمٌ حَكِيمٌۭ

O ye who believe! When there come to you believing women refugees, examine (and test) them: Allah knows best as to their Faith: if ye ascertain that they are Believers, then send them not back to the Unbelievers. They are not lawful (wives) for the Unbelievers, nor are the (Unbelievers) lawful (husbands) for them. But pay the Unbelievers what they have spent (on their dower), and there will be no blame on you if ye marry them on payment of their dower to them. But hold not to the guardianship of unbelieving women: ask for what ye have spent on their dowers, and let the (Unbelievers) ask for what they have spent (on the dowers of women who come over to you). Such is the command of Allah: He judges (with justice) between you. And Allah is Full of Knowledge and Wisdom.

وَإِن فَاتَكُمْ شَىْءٌۭ مِّنْ أَزْوَٰجِكُمْ إِلَى ٱلْكُفَّارِ فَعَاقَبْتُمْ فَـَٔاتُوا۟ ٱلَّذِينَ ذَهَبَتْ أَزْوَٰجُهُم مِّثْلَ مَآ أَنفَقُوا۟ ۚ وَٱتَّقُوا۟ ٱللَّهَ ٱلَّذِىٓ أَنتُم بِهِۦ مُؤْمِنُونَ

And if any of your wives deserts you to the Unbelievers, and ye have an accession (by the coming over of a woman from the other side), then pay to those whose wives have deserted the equivalent of what they had spent (on their dower). And fear Allah, in Whom ye believe.