Adam Clarke on Esther 2:18

Made a release to the provinces - Remitted some kind of tribute or impost, in honor of Esther, at her coronation, as our kings generally do when they are crowned, ordering a discharge from prison of many who are confined for minor offenses. As it was the custom of the Persian kings to give their queens something like what is called with us the aurum reginae, "queen gold," which was a tenth of all fines, etc., above what was given to the king; (for they gave them such a city to buy them clothes, another for their hair, a third for their necklaces, a fourth for their pearls, etc.); it is probable that, on this occasion, Esther so wishing, he relieved those cities and provinces which had before paid this queen gold from all these expenses; and this would tend greatly to make the queen popular.