Esther 3:6-7

3:6 But the thought of striking out against Mordecai alone was repugnant to him, for he had been informed of the identity of Mordecai’s people. So Haman sought to destroy all the Jews (that is, the people of Mordecai) who were in all the kingdom of Ahasuerus.

3:7 In the first month (that is, the month of Nisan), in the twelfth year of King Ahasuerus’ reign, pur (that is, the lot) was cast before Haman in order to determine a day and a month. It turned out to be the twelfth month (that is, the month of Adar).