This second letter of Purim - Mordecai's first letter Esther 9:20 was to some extent tentative, a recommendation. The Jews generally having accepted the recommendation Esther 9:23, Esther 9:27, he and Esther now wrote a second letter which was mandatory.

Esther - wrote with all authority - Esther and Mordecai had the king's license so to do: and their own authority was great and extensive.

Then Esther the queen, the daughter of Abihail, and Mordecai the Jew, wrote with all authority,.... Strongly pressing the observance of this festival; before, Mordecai only recommended it, but now the queen gave a sanction to it, and laid her obligation on the Jews to observe it; perhaps some of the Jews were backward to it, or neglected to observe it, and therefore Esther and Mordecai joined in a letter to them, to press them to it; the Jewish chronologer (x) says, this was written the year following; the former Targum is, they wrote this whole volume, and the strength of the miracle, or set the miraculous deliverance in the strongest light, with this view:

to confirm this second letter of Purim; that it might have its weight and influence upon them, to engage them to keep it, as the latter Targum adds; that when it was an intercalary year, they might not read the Megillah (or book of Esther) in the first Adar, but in the second Adar.

(x) Seder Olam Rabba, c. 29. p. 87.

A second letter from Queen Esther and Mordochai to appoint fasting and lamentation on the days of Purim. Esther 9:29. And Esther the queen and Mordochai the Jew wrote with all strength, that is very forcibly, to appoint this second letter concerning Purim, i.e., to give to the contents of this second letter the force of law. הזּאת refers to what follows, in which the contents of the letter are briefly intimated. The letter is called השּׁנית with reference to the first letter sent by Mordochai, Esther 9:20.

Then Esther the queen, the daughter of Abihail, and Mordecai the Jew, wrote with all authority, to confirm this second letter of Purim.

9:29 Wrote - The former letter, ver.20, did only recommend but this enjoins the observation of this solemnity: because this was not only Mordecai's act, but the act of all the Jews, binding themselves and posterity.

authority: Heb. strength

9:20-32 The observance of the Jewish feasts, is a public declaration of the truth of the Old Testament Scriptures. And as the Old Testament Scriptures are true, the Messiah expected by the Jews is come long ago; and none but Jesus of Nazareth can be that Messiah. The festival was appointed by authority, yet under the direction of the Spirit of God. It was called the feast of Purim, from a Persian word, which signifies a lot. The name of this festival would remind them of the almighty power of the God of Israel, who served his own purposes by the superstitions of the heathen. In reviewing our mercies, we should advert to former fears and distresses. When our mercies are personal, we should not by forgetfulness lose the comfort of them, or withhold from the Lord the glory due to his name. May the Lord teach us to rejoice, with that holy joy which anticipates and prepares for the blessedness of heaven. Every instance of Divine goodness to ourselves, is a new obligation laid on us to do good, to those especially who most need our bounty. Above all, redemption by Christ binds us to be merciful, 2Co 8:9.