Matthew Poole and continuators on Esther 3:7

7 In the first month (that is the month Nisan) in the twelfth year of king Ahasuerus, they cast Pur, that is, the lot, before Haman from day to day, & from month to month , to the twelfth month , that is, the month Adar.

The diviners cast lots, according to the custom of those ancient, and eastern people, what day, and what month would be most lucky, not for his success with the King (of whose compliance with his request he made no doubt) but for the most effectual and universal extirpation of the Jews.

Wherein appears both his implacable malice, and unwearied diligence in seeking vengeance of them with so much, and so long trouble to himself; and Gods singular providence in disposing the lot to that time, that so the Jews might have sufficient space of time to get the decree reversed, as they did.

Marginal references: Chap. 9. 24.