Al-Baqarah 2:229 الطلاق مرتان فامساك بمعروف او تسريح باحسان ولا يحل لكم ان تاخذوا مما اتيتموهن شييا الا ان يخافا الا يقيما حدود الله فان خفتم الا يقيما حدود الله فلا جناح عليهما فيما افتدت به تلك حدود الله فلا تعتدوها ومن يتعد حدود الله فاولايك هم الظالمون ٢٢٩

The divorce is twice, after that, either you retain her on reasonable terms or release her with kindness. And it is not lawful for you (men) to take back (from your wives) any of your Mahr (bridal-money given by the husband to his wife at the time of marriage) which you have given them, except when both parties fear that they would be unable to keep the limits ordained by Allâh (e.g. to deal with each other on a fair basis). Then if you fear that they would not be able to keep the limits ordained by Allâh, then there is no sin on either of them if she gives back (the Mahr or a part of it) for her Al-Khul‘ (divorce)¹. These are the limits ordained by Allâh, so do not transgress them. And whoever transgresses the limits ordained by Allâh, then such are the Zâlimûn (wrong-doers).