Adar II 9

Then Queen Esther daughter of Abihail wrote a second letter of Purim for the purpose of confirming with full authority the aforementioned one of Mordecai the Jew. Dispatches were sent to all the Jews in the hundred and twenty-seven provinces of the realm of Ahasuerus with an ordinance of "equity and honesty": These days of Purim shall be observed at their proper time, as Mordecai the Jew--and now Queen Esther--has obligated them to do, and just as they have assumed for themselves and their descendants the obligation of the fasts with their lamentations. And Esther's ordinance validating these observances of Purim was recorded in a scroll. Esther 9:29-32. The Holy Scriptures according to the Masoretic text, Third Section, The Jewish Publication Society of America, Philadelphia, 1982. Crayon on cardstock; edited on IrfanView.
The footnote in my source says that the ordinance of "equity and honesty" relates to Zechariah 8:19 which reads "Thus said the Lord of Hosts: The fast of the fourth . . . fifth . . . seventh . . . and . . . tenth month [corresponding to the modern 17th of Tammuz, Ninth of Av, Fast of Gedaliah, and Tenth of Tevet] shall become occassions for joy and gladness, happy festivals for the House of Judah; but you must love honesty and integrity." The Prophets, Nevi'im: a new translation of the Holy Scriptures according to the traditional Hebrew text, Second Section, The Jewish Publication Society of America, Philadelphia, 1978. That still made little sense to me until I found a scholarly paper by Albert I Baumgarten. The meaning is: if "modern" fast days can be added to the Jewish calendar (versus older holidays -- those prescribed in the Torah) then surely a joyful holiday that celebrates honesty and integrity can also be added. Amen! Baumgarten also explains that one reason plot features repeat is that this may actually be the dovetailing of two separate stories. This would explain why Esther wrote a dispatch separate from Mordecai's and why she invited Haman and the king to dinner two nights in a row, etc.