Esther 3:2

3:2 As a result, all the king’s servants who were at the king’s gate were bowing and paying homage to Haman, for the king had so commanded. However, Mordecai did not bow, nor did he pay him homage.

Esther 5:14

5:14 Haman’s wife Zeresh and all his friends said to him, “Have a gallows seventy-five feet high built, and in the morning tell the king that Mordecai should be hanged on it. Then go with the king to the banquet contented.”

It seemed like a good idea to Haman, so he had the gallows built.

Esther 10:2

10:2 Now all the actions carried out under his authority and his great achievements, along with an exact statement concerning the greatness of Mordecai, whom the king promoted, are they not written in the Book of the Chronicles of the Kings of Media and Persia?