Ester 9:31

31 to establish these days of Purim at their designated times, as Mordecai the Jew and Queen Esther had decreed for them, and as they had established for themselves and their descendants in regard to their times of fasting and lamentation.

31 Giving the force of law to these days of Purim at their fixed times, as they had been ordered by Mordecai the Jew and Esther the queen, and in keeping with the rules they had made for themselves and their seed, in connection with their time of going without food and their cry for help.