Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) said regarding this saying of Allah Almighty: "And if you divorce them before you have touched them, while you have already specified for them a dower, then pay half of what you specified" [Surah al-Baqarah: 237]: When a man, after marriage, divorces before consummation while the dower (mahr) has been specified, then the woman is due half the dower, and no more.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصداق / 14475