The Talmud in TRACTATE MEGILLAH (10b,11a) cites various verses with which a number of Talmudic rabbis began their Purim sermons. It cites R. Levi has having opened with the following: "Now if you will not drive out the inhabitants of the land etc." (Bamidbar 33:55). The verse continues that they will become ....as thorns in your sides and they will (constantly) oppress you in the land on which you dwell:

How, we may ask, does R.Levi’s opening verse, which deals with the initial conquest of the Land of Israel, relate particularly to the Purim story.

I believe the point of R. Levi was to offer a truism regarding our dealings with our enemies in general, that would therefore apply, even more so, to our eternal nemesis Amalek. The lesson is that one cannot ‘dilly-dally’ with those that are out to destroy us. Once we identify them as clear adversaries, we must act decisively and with the firmest resolve against them. If not, things will not get better but will consistently deteriorate to the point that they will be an ongoing thorn in our side. This principle is seen vividly in the Purim story when Mordechai urges Esther to act on Klall Yisrael’s behalf. She answers that things will have to wait a while as she is not scheduled to be summoned to the king for another thirty days. To which Mordechai responds: If you shall remain silent at this present time....you and your household will be lost... and who knows if it was not for this moment that you attained royalty." The message undoubtedly penetrated since we see that from that moment on Esther acts with great resolve, thereby saving the day by successfully ridding us of Haman and his murderous decree.

R. Levi’s message is a most crucial one for our times where we often fail to identify evil, and certainly fail to act against it with firm resolve. It is R. Levi’s general lesson that when we do this, things only tend to deteriorate further. When, however, we are firm and resolute, then with G-d’s help, victory over our adversaries is surely at hand.