“Queen Esther daughter of Abihail, along with the Jew Mordecai, were given full written authority. They confirmed this second letter about Purim. Letters were sent wishing peace and security to all the Jews, to the one hundred twenty-seven provinces of the kingdom of King Artaxerxes. This letter gave orders that these days of Purim should be observed at their appointed seasons. The Jew Mordecai and Queen Esther enjoined on all the Jews, just as they had for themselves and for their descendants, regulations concerning their fasts and their lamentations. The command of Queen Esther fixed these practices of Purim. It was recorded in writing.”
Not only was there an explanation by Mordecai, the queen herself sent out a letter to the 127 provinces pertaining to all the Jews. Purim was to be observed at the appointed times. She laid out the regulations concerning this feast, with fasting, and lamentations. All of this was in writing. Once again there was an insistence that this was written down. The feast of Purim would become an important post-exilic feast day, a time of great rejoicing, drinking and eating.
Eugene Finnegan Bible Project 