Haman decided first to consult with astrologists and other diviners. Whatever his religion may have been (there were many religions in the Persian Empire, and they were all basically tolerated), it clearly included the typically pagan belief in lucky and unlucky days. A great undertaking, such as the massacre of all the Jews in the empire, had to take place on the right day. This could only be revealed through divination.
It is ironic that the lot for the day of Israel’s destruction was cast in the month of Nisan. This was the month during which they were celebrating their deliverance from Egypt.
We do not know exactly how these diviners would have cast the lot. It may have taken them a long time to arrive at the lucky day for the massacre. It was only when they came to the twelfth month of the year, the month of Adar, that such a day was found.
This meant that Haman had to wait for a whole year! It would demand all his patience and self-control, as Mordecai continued to show disregard for him, day by day (Esther 5:9).
Although this lot was cast in a pagan and superstitious manner, it still serves as a powerful illustration of the truth that the lot is cast into the lap, but its every decision is from the Lord
(Proverbs 16:33). God caused the lot to fall on the last month of the year, thereby giving Esther and her people the time needed to respond.
7 In the first month, which is the month of Nisan, in the twelfth year of King Ahasuerus, they cast Pur (that is, they cast lots) before Haman day after day; and they cast it month after month till the twelfth month, which is the month of Adar.