Our Talmudic sages stress that no word in the Torah is insignificant. Rather, every word, indeed every letter, has rhyme and reason. An extension of this axiom is that no word in the Torah is redundant. What at first glance appears repetitious is not, but in fact has a different connotation than the word it seems to be repeating.
A poignant example of the above teaching is found in Parshat Zachor, the Maftir of this Shabbat. Hashem bids us זכור -- remember what Amalek did to us. The paragraph continues with a detailed description of Amalek's attack, further bids us to obliterate Amalek's descendants, and then concludes with the words לא תשכח-- do not forget. Our sages ask a simple question: Aren't the commands to "remember" and to "not forget" the event one and the same? While normally this may be the case, in the Torah this can not be so, for there are no redundant words in the Torah. How, then, do the two dicta of זכור and לא תשכחdiffer?
Our rabbis explain that the negative command לא תשכח is to remember in one's heart -- remembering in its most literal sense. The positive command זכור, however, is to remember and proclaim with one's lips. "לא תשכח" is passive remembering, whereas "זכור" is active remembering. The dictum "זכור" thus serves as the source for the rabbinic (or perhaps biblical) command to read Parshat Zachor, as we are commanded to not only remember but also to proclaim Amalek's actions against us. (The word "זכור" in this pasuk gives us the meaning of the other instances of this word in the Torah -- it is always understood as a call to active remembering. One such example is the recitation of Kiddush on Shabbat. The Torah simply states "זכור" -- Remember the Shabbat. Our sages inform us that here too "זכור" implies proclaiming and not merely remembering in one's heart, hence the mitzvah to recite Kiddush).
Let us turn to another linguistic issue in Parshat Zachor. Several years ago I was privileged to participate in an interdenominational community-wide rally in support of the American troops fighting the Gulf War. After the introductory remarks by the host rabbi and the benediction by myself, a Reform Rabbi delivered the "Dvar Torah." His point: We dare not take literally the command "תמחה את זכר עמלק" -- obliterate the memory of Amalek. God forbid, he explained, that the Torah would demand of us to wipe out an entire nation based on the actions of their ancestors. The rabbi proceeded to "prove" his point from the text by explaining that there is a contradiction between זכור""-- "remember", on one hand, and "תמחה את זכר"-- "obliterate the memory," on the other. It is obvious, he therefore concluded, that there is no command to literally destroy Amalek. (Interestingly, the rabbi did not offer an alternative explanation of the verse in question.)
Aside from the fact that the rabbi was incorrect from a halachic perspective, he was also incorrect from a linguistic perspective. Rabbi Don Well (in an essay published in Or Shumuel, a Torah journal of the Hebrew Theological College) suggests that there is a difference in meaning between the word זכרון and זכר. Both have the connotation of memory, but a זכרון is merely a reminder, whereas a זכר is a remainder. This explains why Hashem commanded Yehoshua כתב זאת זכרון -- record the incident of Amalek as a reminder, for the recording of an event serves as a reminder of that event. In Parshat Zachor, however, we are bidden תמחה את זכר עמלק -- obliterate the remainder of Amalek. There is therefore no contradiction between זכור, the command to recall the actions of Amalek, and the command to wipe out the זכר, the remaining descendants of Amalek.
One final point. Rashi (דברים כה:יז) is of the opinion that our ancestors were attacked by Amalek because they were unscrupulous in their business practices. He further asserts that if one cheats in business, he should worry that the enemy might attack, i.e. he will be punished for his actions. "Those who forget the lessons of history are destined to repeat it". We must forever recall not only the incident of Amalek, but also the lesson to be learned from it. Instead of having to be punished by Hashem for our mistreatment of others, let us deserve to be rewarded for our meritorious respect of one another. As we celebrate Purim, may we engage solely in actions that promote the welfare of our brethren, as did Mordechai and Esther.