Woman need not return back her Mahar
If want to remarry a woman, after divorcing the previous wife. If you have given a heap of wealth to the previous wife, don’t snatch away anything from it. While you are in guilty and injustice do you try to snatch it away also?
(Al-Quran 4:20)
While you have made a solemn covenant and mingled with each other, how can you snatch it away from her?
(Al-Quran 4:21)
You cannot demand Mahar on any occasion.
Thus divorcing is allowed twice only. After that either they hold together or separate from each other permanently, you have no right to get back anything what you have given to them. While they are living together, if they afraid they cannot maintain the limits ordained by Allah and she give back something for her freedom and there is no blame on both of them. These are the limits ordained by Allah. Do not transgress it. Those who transgress the limits are in guilt and injustice.
(Al-Quran 2:229)