Surat Al-Mumtaĥanah - سورة الممتحنة

وَإِن فَاتَكُمْ شَيْءٌ مِّنْ أَزْوَاجِكُمْ إِلَى الْكُفَّارِ فَعَاقَبْتُمْ فَآتُوا الَّذِينَ ذَهَبَتْ أَزْوَاجُهُم مِّثْلَ مَا أَنفَقُوا ۚ وَاتَّقُوا اللَّهَ الَّذِي أَنتُم بِهِ مُؤْمِنُونَ

Muhsin Khan: And if any of your wives have gone from you to the disbelievers, and you have an accession (by the coming over of a woman from the other side), then pay to those whose wives have gone, the equivalent of what they had spent (on their Mahr). And fear Allah in Whom you believe.