Esther 9:21

To stablish this among them,.... That it might be a settled thing, and annually observed in all future generations, what they had now done:

that they should keep the fourteenth day of the month Adar, and the fifteenth day of the same, yearly; as the former had been observed by the Jews in the provinces, and both by those in Shushan, Esther 9:17

as festivals in commemoration of their great deliverance; hence the fourteenth of Adar is called the day of Mordecai, being established by him;

"And they ordained all with a common decree in no case to let that day pass without solemnity, but to celebrate the thirtieth day of the twelfth month, which in the Syrian tongue is called Adar, the day before Mardocheus' day.'' (2 Maccabees 15:36)