Esther 3:10

3:10 So the king removed his signet ring ¹  from his hand and gave it to Haman the son of Hammedatha, the Agagite, who was hostile toward the Jews.

Esther 8:2

8:2 The king then removed his signet ring (the very one he had taken back from Haman) and gave it to Mordecai. And Esther designated Mordecai to be in charge of Haman’s estate.

¹ sn Possessing the king’s signet ring would enable Haman to act with full royal authority. The king’s ring would be used to impress the royal seal on edicts, making them as binding as if the king himself had enacted them.