In this week's parsha we read about Amalek's infamous attack on Bnei Yisrael when they left Mitzraim. It is therefore important and relevant to discuss the Halachot concerning the mitzvah to recall the actions of Amalek. The source for this mitzvah can be found in דברים פרק כה פסוק יז which states זכור את אשר עשה לך עמלק בדרך בצאתכם ממצרים. This pasuk teaches us about the positive mitzvah associated with commemorating מעשה עמלק which is זכירה , remembering the event. However there is also a negative commandment of לא תשכח (דברים כה:יט) that we are not allowed to forget what Amalek did to us. The Gemara (מגילה יח.) describes the מצוות עשה of Zachor as relating to one's mouth, with the telling and talking about Amalek's attack, while the issue of forgetting is associated with one's heart, that one must never forget מעשה עמלק. To fulfill the mitzvah of זכור, one must remember Amalek's infamous attacks on us when we came out of Mitzrayim and their hatred towards us (ספר החינוך מצוה תר"ג, and see Encyclopedia Talmudit 21:712 note 7). The ספר החינוך gives us one explanation as to why we must never forget what Amalek did. He asserts that they are our worst enemy because until they attacked, all the other nations were afraid to even engage Bnei Yisrael in battle. However, after Amalek's attack, even though they were defeated, the other nations lost their fear of Bnei Yisrael. The Midrash Tanchuma gives a mashal to explain this reasoning. There was a barrel of boiling hot water so hot that everybody was afraid of going in. Then one person jumped in, and even though it was just as hot, everybody else was no longer afraid to go in (see Rashi to דברים כה:יח).
Why should we be obligated in the Mitzvah of זכור today if we cannot do any harm to Amalek, since we do not know if they still exist or who they are? The answer given by the מלאכת שלמה is that even after Moshiach comes and Amalek is totally wiped out, we still have the מצווה of זכור because the purpose of this Mitzvah is to remember what caused Amalek to attack. Our sins are what caused Amalek to attack (see דברים כה:יח)! The purpose of the Mitzvah is to remember the effects of our sins in order that we will avoid repeating them. In addition, Rabbi Joseph B. Soloveitchik (in his essay קול דודי דופק) cites his father's opinion that anyone who adopts the idealogy of Amalek (attacking Jews for no reason) is considered to have the status of an Amalekite despite the fact that he is not a biological descendant of Amalek. Rabbi Soloveitchik believed that the Nazis had the halachic status of עמלק (see נפש הרב p. 78) Rabbi Howard Jachter reports that Rabbi Soloveitchik told him that one who studies the history of Nazi Germany has fulfilled the mitzvah of remembering Amalek (but not as a replacement for remembering the actual descendants of Amalek).
There are some great authorities who do not include זכור or לא תשכח in their listing of the 316 mitzvot. They include the בה"ג, the יראים, and רב סעדיה גאון. These authorities believe that the mitzvah to remember Amalek is a part of the mitzvah to destroy Amalek, and it is not an independent mitzvah. Other lists of 316 Mitzvot only include זכור and not the prohibition of לא תשכח. The סמ"ג explains the rationale for this exclusion is that the purpose of לא תשכח is dependent on the positive commandment of זכור. In other words, the Mitzvah of לא תשכח is not to forget the Mitzvah of זכור.
Those Rishonim (Rambam, Smag and Chinuch) who believe that זכור is an independent Mitzvah state that in order to fulfill the Mitzvah one has to read פרשת עמלק (found in כי תצא כה:יז-יט) on the Shabbat before Purim. In other words, that קריאה בציבור is the way to fulfill one's obligation of זכירת מעשה עמלק. The Tosafot, Rosh, and Rashba (in their respective commentaries in ברכות יג.) write that the obligation of reading Parshat Zachor is מדאוריתא, from the Torah. There are even some Rishonim (תרומת הדשן סימן נח) (e.g. the Sefer HaEshkol) who say that מדאורייתא one has to hear Parshat Zachor read from a Sefer Torah and together with a minyan. The Pri Migadim (אורח חיים קמג:א) holds that if one read the Parsha of Zachor and then found a deficiency in the Torah, one must take out a new sefer Torah and reread the Parsha of Zachor.
According to the Ramban, in his commentary to Chumash at the end of Parshat Ki Tetze, the Rishonim who hold that, מדאורייתא, a minyan is mandatory for the mitzvah of זכור, must hold that there is a basis (סמך) in the Torah for Megillah reading. Since Purim is celebrated because of destroying Amalek (that Haman and the others who attempted to kill the Jews were killed), the Megilla reading is a form of זכירת עמלק, which is a חיוב מדאורייתא. The Ramban's own opinion, however, is that מדאורייתא there is neither a Mitzva to read with a minyan, nor must the Parsha of zachor be read on the Shabbat before Purim. A question that one could ask about this opinion is why does the Torah make a set time to remember leaving Egypt (in the morning and at night) and not for remembering Amalek? Those rishonim explain that remembering Amalek is different than remembering יציאת מצרים, because unlike the latter, which is a basic principle upon which Judaism is based, the only purpose of remembering Amalek is that we do not forget our hatred of them. Therefore, the Torah does not make a set time for זכירת עמלק, rather it is sufficient to remember this once a year.
The Magen Avraham (ס' תרפה) and other Achronim (see Encyclopedia Talmudit 21:022 note 04) believe that if one hears the Parsha of ויבא עמלק (from the end of this week's parsha) on Purim one fulfills the mitzvah of remembering Amalek מדאורייתא, since by hearing it one remembers the actions of Amalek. The Mishna Berurah (תרפה:טז) disputes this ruling. He says that one cannot fulfill this Mitzvah by reading ויבא עמלק since these Pesukim do not mention an obligation to destroy עמלק.
A question raised is why do we perform the Mitzvah of Zechirat Amalek only once a year? Why not more often? The answer found at the end of the work מיני תרגימא is that when the Chumash states לא תשכח, we are to understand that what constitutes forgetting is twelve months. We learn this from Tehillim (לא:יג) which states נשכחתי כמת מלב הייתי ככלי עובד, or the rule that a lost vessel is forgotten by someone after twelve months (and see Rashi's explanation on ברכות נח: and בבא מציעא כח.).
By contrast, the Minchat Chinuch (מצוה תר"ג) believes that the opinion of the ספר החינוך is that to fulfill one's obligation of זכירה מדאורייתא, one only has to remember the actions of Amalek once in a lifetime. The obligation of זכירת עמלק once a year and with a minyan and a Sefer Torah is מדרבנן. The Minchat Chinuch adds that if one only did zechira in his heart, without talking (using one's mouth), he has not fulfilled the positive command, though one is not transgressing the negative prohibition. This is based on the aforementioned quote from מגילה יח. The Rambam (הלכות מלכים ה:ה), on the other hand, rules that one must constantly (תמיד) remember the actions of Amalek. Rabbi Jachter reports that Rav Aharon Lichtenstein argues that reading the Parsha of Amalek yearly is considered to be remembering Amalek constantly.
A vitally important question is whether women are obligated in the Mitzvah of זכירת מעשה עמלק. The Sefer HaChinuch holds that the Mitzvah only applies to men; since men were given the Mitzvah of fighting and destroying Amalek, only they have the Mitzvah of זכור (women do not go to war, see יבמות סה:). According to the Minchat Chinuch, women are also not obligated in the negative commandment of לא תשכח. A number of Acharonim including the בנין ציון (שו"ת חדשות סימן ח'), מנחת חינוך and the Torat Chesed (אורח חיים סימן לז) assert that the Rambam and Ramban disagree with this opinion of the ספר החינוך. The Acharonim assert that both Rambam and Ramban hold that women are obligated in the Mitzvah because the only time that women are not obligated in a Mitzvah is when it is a מצות עשה שהזמן גרמא (time bound mitzva), and this is not one of those Mitzvot (the Rambam writes that one must constantly remember the acts of Amalek). Furthermore, they should be forbidden to forget Amalek (לא תשכח), because women are rarely פטור from any prohibitions. In addition, one cannot say that women are not obligated in this Mitzvah because they are not obligated to fight in a war, because the Mishna in סוטה מד:() states that women are obligated in מלחמות מצוה, which the fight against Amalek certainly is (see Rambam הלכות מלכים ה:א). The Torat Chesed points out that Rambam and other Rishonim believe that Zechirat and Mechiat Amalek are two totally separate Mitzvot. It follows that even if women were not obligated in destroying Amalek because they did not wage war, they still would be obligated in זכור. The Torat Chesed also asserts that according to the opinion that states that the communal Torah reading of Parshat Amalek is מדאורייתא, women are obligated to listen. However, according to the Poskim who believe that the communal Torah Reading of Parshat Amalek is a Rabbinic decree, the Rabbis instituted the obligation to read פרשת זכור only for men. According to this approach, women would fulfill their obligation just by reading the Parsha of Amalek in a Chumash. In addition, Rabbi Yissachar Frand of Yeshivat Ner Yisrael has suggested that perhaps even the Mishna Berurah would agree with the Magen Avraham that women can fulfill their obligation by listening to the Torah reading of ויבא עמלק from this week's Parsha. The Mishna Berurah objected to the Magen Avraham's view because ויבא עמלק does not contain an exhortation to eliminate Amalek. Rabbi Frand argues, though, that since women have the obligation to remember Amalek and not wage war, listening to ויבא עמלק would suffice to discharge their obligation to remember Amalek. According to this approach, this week women can fulfill the Mitzva of זכור and men cannot.
Let it be our hope that Mashiach comes soon, and that we will finally come to see a total destruction of all the Amaleikim in the world, and that all evil in the world will be eliminated.