Esther 3:7-8

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).

3:8 Then Haman said to King Ahasuerus, “There is a particular people that is dispersed and spread among the inhabitants throughout all the provinces of your kingdom whose laws differ from those of all other peoples. Furthermore, they do not observe the king’s laws. It is not appropriate for the king to provide a haven for them.

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 6:4

6:4 Then the king said, “Who is that in the courtyard?” Now Haman had come to the outer courtyard of the palace to suggest that the king hang Mordecai on the gallows that he had constructed for him.