وَإِن طَلَّقْتُمُوهُنَّ مِن قَبْلِ أَن تَمَسُّوهُنَّ وَقَدْ فَرَضْتُمْ لَهُنَّ فَرِيضَةً فَنِصْفُ مَا فَرَضْتُمْ إِلَّا أَن يَعْفُونَ أَوْ يَعْفُوَ الَّذِي بِيَدِهِ عُقْدَةُ النِّكَاحِ ۚ وَأَن تَعْفُوا أَقْرَبُ لِلتَّقْوَىٰ ۚ وَلَا تَنسَوُا الْفَضْلَ بَيْنَكُمْ
“If you divorce them before you have touched them, while you have already fixed for them an amount of dowry, then there is one half of what you have fixed, unless they (the woman) forgive or forgives the one in whose hand lies the marriage tie, and it is closer to taqwa (righteousness) that you forgive, and do not forget to be graceful to one another.” (Surah Baqarah, v237)
If the dowry was not stipulated and the wife was divorced or the husband died, and this was after consummation, she will receive the standard dowry received by other women of her family. If there was no consummation, but the dowry was stipulated, she is entitled to half the agreed amount. There will naturally be no issue if she chooses to waive the entire amount or he chooses to give the full sum. If the dowry was specified and the marriage was consummated, the full sum will be due from the husband.