Quran 60:10

يَـٰٓأَيُّہَا ٱلَّذِينَ ءَامَنُوٓاْ إِذَا جَآءَڪُمُ ٱلۡمُؤۡمِنَـٰتُ مُهَـٰجِرَٲتٍ۬ فَٱمۡتَحِنُوهُنَّ‌ۖ ٱللَّهُ أَعۡلَمُ بِإِيمَـٰنِہِنَّ‌ۖ فَإِنۡ عَلِمۡتُمُوهُنَّ مُؤۡمِنَـٰتٍ۬ فَلَا تَرۡجِعُوهُنَّ إِلَى ٱلۡكُفَّارِ‌ۖ لَا هُنَّ حِلٌّ۬ لَّهُمۡ وَلَا هُمۡ يَحِلُّونَ لَهُنَّ‌ۖ وَءَاتُوهُم مَّآ أَنفَقُواْ‌ۚ وَلَا جُنَاحَ عَلَيۡكُمۡ أَن تَنكِحُوهُنَّ إِذَآ ءَاتَيۡتُمُوهُنَّ أُجُورَهُنَّ‌ۚ وَلَا تُمۡسِكُواْ بِعِصَمِ ٱلۡكَوَافِرِ وَسۡـَٔلُواْ مَآ أَنفَقۡتُمۡ وَلۡيَسۡـَٔلُواْ مَآ أَنفَقُواْ‌ۚ ذَٲلِكُمۡ حُكۡمُ ٱللهِ‌ۖ يَحۡكُمُ بَيۡنَكُمۡ‌ۚ وَٱللَّهُ عَلِيمٌ حَكِيمٌ۬ ١٠

O you who believe, when believing women (abandon the enemy and) ask for asylum with you, you shall test them. ALLAH is fully aware of their belief. Once you establish that they are believers, you shall not return them to the disbelievers. They are not lawful to remain married to them, nor shall they (the disbelievers) be allowed to marry them. Give back the dowries that they (the disbelievers) have paid. You commit no error by marrying them, so long as you pay them their due dowries. Do not keep disbelieving wives (if they wish to join the enemy). You may ask them for the dowry you had paid, and they may ask for what they paid. This is ALLAH’s rule; He rules among you. ALLAH is Omniscient, Most Wise.