The Shabbat just preceding Purim is called “Shabbat Zakhor” because the Torah reading on that day ends with the commandment of Deut 25:17-19:
Remember what Amalek did to you on your way out of Egypt—how he fell on you along the way, attacking the weakest among you, those who were straggling at the rear, when you were tired and weary; he lacked all common decency. When the LORD your God gives you relief from all the enemies around you, in the land that the LORD your God gives you to keep as a homeland, blot out the memory of Amalek from under the heavens—do not forget!
The connection of these verses with the celebration of Purim is straightforward enough. The villain of the Purim story, Haman, is first introduced as “Haman the son of Hammedatha the Agagite” (Esther 3:1). The word “Agagite” seems to refer to a particular descendant of Amalek, the Amalekite king Agag (1 Sam 15:8). If Haman himself was related to King Agag, this would mean that he too was a descendant of Amalek and someone who, just like Amalek, tried to do great harm to the people of Israel. (How a descendant of a fierce nomadic tribe in the Negev ended up as an emperor in faraway Persia is certainly a good question…but certainly stranger things have happened in history.)
However, the commandment that ends this passage in Deuteronomy seems to contain a contradiction. How can we be commanded to blot out Amalek’s memory and in the same breath be told “do not forget”: how can one simultaneously erase a memory and preserve it?
The problem is primarily one of translation. It is true that Hebrew zekher sometimes means “memory” or “memorial.” But it has another meaning as well: a person’s name. Thus, when God reveals his name to Moses on Mount Horeb, He concludes by saying, “this is My name (shemi) forever, and this is My appellation (zikhri) for all generations” (Exod 3:15). Similarly, the expression “a righteous man’s zekher is for a blessing” (Prov 10:7) means that when a person wishes to bless someone, he often does so by invoking the name of a righteous man (e.g. “May you be like Abraham”). So, when the Torah commands Israelites to “blot out the zekher of Amalek,” it means: blot out his name. This expression is the equivalent of saying: kill him and all his descendants, so that there will no more be anyone who bears the name of Amalek. (See the same expression used in the same sense in Deut 9:14 and 29:19, 2 Kings 14:27, Ps 9:6, etc.)
But if so, hasn’t this commandment already been carried out to the fullest? The very last Amalekite anyone has heard of was Haman himself: since then, the name of “Amalek” has apparently disappeared forever. If so, why do we read this passage year after year?
Various answers to this question have been proposed, but the most straightforward would seem to be that of Ramban (R. Moshe b. Nahman, or Nahmanides): He writes that the Torah’s commandment is for us “to recount this [story] to our children and our descendants, telling them that this is what this wicked man did to us, and that is why we were commanded to blot out his name.” In other words, we were first commanded to blot out the name of Amalek until he had no descendants; but we were further commanded to tell the story to later generations, “telling them that this is what this wicked man did to us.” In this sense, Amalek became an ongoing warning, a symbol and a prototype.
To which it is necessary these days to add that Amalek is not a symbol of non-Jews in general, but only of those (usually few) people who are actually intent on doing us harm. Such people do exist, but if you are incapable of distinguishing them from other people who are not hostile, people who, in fact, may be altogether friendly, then all you are doing is preventing true enemies from being identified as such. One of the dumbest things I hear nowadays, especially in Israel, is “the whole world is against us”( כל העולם נגדנו). Actually, this seems to be the opposite of Ramban’s understanding of the Torah’s commandment: tell the story so that, when someone similar comes along, you’ll know.