Esther 9:23 (ESV)

23 So the Jews accepted what they had started to do, and what Mordecai had written to them.

The Jews respected Mordecai’s leadership and agreed to institute this new feast, just as he had ordered. In this regard, the Purim feast differs from other biblical feasts, such as the Passover, Feast of Weeks, and Feast of Tabernacles. These feasts, together with the Sabbaths and Sabbath years, were instituted by God himself. The Purim was instituted by Mordecai, in response to a new situation. It may be compared with Christian feast days such as Christmas, Good Friday, and Ascension, and even Reformation Day.