Sura al-Mumtaḥanah 60:11

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

wa-in fātakum shayʾun min azwājikum ilā l-kuffāri fa-ʿāqabtum fa-ātū lladhīna dhahabat azwājuhum mithla mā anfaqū wattaqū allāha alladhī antum bihi muʾminūna

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.