TSK · Esther 3:12

Then they presented the decrees of the king to the king’s satraps and to the governors of Trans-Euphrates, who gave help to the people and to the temple of God.

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.

Mordecai wrote in the name of King Ahasuerus and sealed it with the king’s signet ring. He then sent letters by couriers on horses, who rode royal horses that were very swift.

Now let the king issue a written interdict so that it cannot be altered, according to the law of the Medes and Persians, which cannot be changed.”

Then those men came by collusion to the king and said to him,“Recall, O king, that it is a law of the Medes and Persians that no edict or decree that the king issues can be changed.”