Midrash su Ester 9:1

And it came to pass in the days of Ahasuerus. R. Levi said: "He was the brother of a head and the coeval associate of a head. The brother of a head, i.e., the brother of Nebuchadnezzar, the wicked, who was called head, as it is said (Dan. 2, 38) Thou art the godhead. And the coeval associate of a head — what Nebuchadnezzar had done, he had intended to do. Nebuchadnezzar had killed, he had intended to kill; Nebuchadnezzar had destroyed; he had the intention, and so reads the passage (Ezra 4, 1) In the beginning of the reign of Ahasuerus, they wrote slanders on the inhabitants of Judea and Jerusalem." Samuel said: "[Ahasuerus has the meaning of black i.e.] in his days the faces of the Jews were black as the bottoms of pots." R. Chanina said: "[Ahasuerus has the meaning of 'woe to his head' (Ach rosh). Whoever mentioned his name said 'Woe to his head.' " R. Jochanan said: "[It has the meaning of 'poor' (rosh)] His taxes were so heavy that men became poor, as it is said (Est. 9, 1) And King Ahasuerus imposed a tribute upon his land." (Ib. 1)

What is the day of assembly? It was said: The thirteenth of the month of Adar is the day of assembly, as it is written: On the thirteenth day the Jews assembled in their cities (Est. 9:1–2). That is, they assembled on that day and decreed that the thirteenth day of Adar should be a fast-day, However, they designated the fourteenth day of Adar as a festive day, as it is written: And on the fourteenth day they rested and made it a day of feasting and gladness (ibid., v. 17).

Haman wanted to destroy all the Jews, but the Holy One, blessed be He, did not desire it, and therefore: Whereas it was turned to the contrary, that the Jews ruled over them that hated them (Est. 9:1). Balaam and Balak wanted to curse Israel, but the Holy One, blessed be He, did not agree, as it is said: Nevertheless, the Lord thy God will not hearken unto Balaam (Deut. 23:6). Hence it is said: Who is he that saith, and it came to pass, when the Lord commandeth it not? (Lam. 3:37). Hadrian said to R. Joshua: “Mighty is the lamb that can survive among seventy wolves.” And he replied: “Mighty is the shepherd who can save and protect the lamb, and destroy the wolves surrounding her.” Therefore, it is written: No weapon that is formed against thee shall prosper (Ps. 54:17).