Esther 3:10

3:10 So the king removed his signet ring from his hand and gave it to Haman the son of Hammedatha, the Agagite, who was hostile toward the Jews.

Esther 8:8

8:8 Now you write in the king’s name whatever in your opinion is appropriate concerning the Jews and seal it with the king’s signet ring. Any decree that is written in the king’s name and sealed with the king’s signet ring cannot be rescinded.