Esther 3:8

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 5:7

5:7 Esther responded, “My request and my petition is this:

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.