Devarim 25, 17-19
Remember what Amaleik did to you on your way out of Egypt.
When they happened upon you on the way, and you were tired and exhausted, they cut off those lagging to your rear, and they did not fear God.
Therefore, when Hashem gives you peace from all the enemies around you in the land that Hashem your Hashem is giving you to occupy as a heritage, you must obliterate all reminders of Amaleik from under the heavens. You must not forget.
This notion that Purim explains the way to make a change permanent ties in with a thought on Parshas Pekkudei. There is a famous Aggadita that explains why Moshe Rabbeinu could not be the one to take us into Eretz Yisrael. Anything Moshe did is permanent. This is important, because if it were possible to abrogate one thing that he did, it brings into question the permanence of the Torah. However, Hashem knew that the time would come when the Jews would deserve punishment. By having Yehoshua bring us into Israel, it made the choice of exile a possible punishment.
The eighth day also parallels the Third Beis Hamikdosh, which will never be destroyed. Moshe was not merely participating in the consecration of the Mishkan, but also was demonstrating the permanence of the Messianic age. The Temple will not fall again; there will be no more exiles.
We find that Hashem uses two adjectives to describe Moshe. The first is anav, modest.
The second, is that Hashem calls him “Moses My servant”, Moshe Avdi. “Moshe avdi is not like that” (ibid 7). Rabbiner Hirsch finds a similarity between Eved, with an Ayin, and Avad, with an Aleph. Avad means lost. Eved, with the voiced ayin instead of the silent aleph, means one whose will, desires, and self-identity are occluded by another’s. Moshe Avdi, therefor, means, Moshe, who made his desires secondary to Mine.
Both adjectives, anav and eved, describe Moshe Rabbeinu as one who placed his own desires second. Everything Moshe did was l’sheim Shamayim (for the sake of heaven). His actions were an expression of Hashem’s will.
R. Yochanan HaSandler (Avos 4:14) describes what gives permanence to a congregation.
Any congregation which is l’sheim Shamayim will end up existing, and congregation which is not lesheim Shamayim will not end up existing.
And so, Esther too explains that road to real, permanent, change.