Esther 8:13 (ESV)

13 A copy of what was written was to be issued as a decree in every province, being publicly displayed to all peoples, and the Jews were to be ready on that day to take vengeance on their enemies.

By making the edict known to all the peoples of the Persian empire, it would be clear to everyone where the king’s sympathy now lay. Moreover, no one would try to hinder the Jews from preparing for counterattack.