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 7:9

7:9 Harbona, one of the king’s eunuchs, said, “Indeed, there is the gallows that Haman made for Mordecai, who spoke out in the king’s behalf. It stands near Haman’s home and is seventy-five feet high.”

The king said, “Hang him on it!”