The Sages instituted the reading of Parashat Zakhor once a year in order to fulfill the Torah commandment to remember and not forget the evil deeds of Amalek. One is viewed as having forgotten about Amalek only if a year goes by without remembering it. Therefore, we discharge our obligation by mentioning the matter once a year. We read Parashat Zakhor on the Shabbat before Purim in order to juxtapose remembering Amalek to the destruction of his descendant Haman.
According to Torah law, one must express this remembrance verbally. There is no need, however, for every individual to read Parashat Zakhor from a Torah scroll; rather, everyone fulfills the mitzva by hearing another person read the verses from the Torah.
According to some of the greatest Rishonim, the Torah commands us to read Parashat Zakhor from the Torah scroll itself. Therefore, it is proper to read it from an exceptionally beautiful Torah scroll, and the reader must try to read the passage as meticulously as possible.
Preferably, everyone should hear Parashat Zakhor read according to his family’s accepted traditions of cantillation and pronunciation. Technically, however, members of all Jewish communities can discharge their obligation by hearing it read according to any version accepted among the Jewish people, whether it is Sephardic, Ashkenazic, or Yemenite.
One who finds himself in a place where there is no minyan should read Parashat Zakhor from a Torah scroll without a minyan. If no Torah scroll is available, he should read it from a ĥumash or a siddur.
Mitzvot require kavana (focused intent); therefore, one must have in mind to fulfill the mitzva of remembering Amalek’s deeds when reading or hearing Parashat Zakhor. It is a good practice for the gabbai or reader to announce this before commencing the reading.
. One must mention Amalek verbally. After all, the Sages understood that the mitzva not to forget what Amalek did to us commands us to remember internally (Megilla 18a). Thus, when the Torah commands us to remember, it means through verbalization. The poskim dispute what exactly the Torah obligation entails. Rambam and Ramban imply that reading from a Torah scroll is a rabbinic enactment, and that by Torah law one fulfills the mitzva by reading from a ĥumash or through any other means of commemoration. (Marĥeshet 1:22 states, based on Ramban’s commentary on the end of Parashat Ki Tetzei, that reading the megilla on Purim also fulfills the mitzva of remembering Amalek.) On the other hand, according to Tosafot, Rashba (Ber. 13a), Rosh, and Eshkol, one is obligated by Torah law to hear Parashat Zakhor read from a Torah scroll. sa 146:3 rules in accordance with this opinion. Therefore, we bring a Torah scroll to a sick person or a prison inmate in order to read Parashat Zakhor for him, an action that we do not take for any other reading (mb 135:46; see also bhl ad loc.).
If the scroll from which Parashat Zakhor was read is later found to be invalid, there is no need to reread the parsha from a different scroll (Halikhot Shlomo 18:4), because, according to several poskim, one fulfills the mitzva without a Torah scroll, and others maintain that a Torah scroll is required, but that one fulfills his obligation with an invalid Torah scroll. It stands to reason that if the defect in the scroll is found on that same Shabbat, the congregation should reread Parashat Zakhor from a valid scroll, since the Sages instituted the reading on that particular day.
Terumat Ha-deshen §108 infers from Rosh that according to Torah law, the mitzva to read Parashat Zakhor can only be fulfilled by reading the passage from a Torah scroll in the presence of ten men. Several Aĥaronim explain that by remembering what the Amalekites did to us, we become aroused to wage war against them, and since war is a communal obligation, Parashat Zakhor must be read with the congregation (Keren Ora, Maharam Schick). It seems to me that even Terumat Ha-deshen agrees that in the absence of a congregation there is still a mitzva to read it individually. sht 685:5 expresses puzzlement about Terumat Ha-deshen’s viewpoint and states that all other Rishonim maintain that a minyan is required only rabbinically. In practice, if one finds himself in a place where there is no minyan, he should read Parashat Zakhor privately from a Torah scroll. If no scroll is available, he should read it from a ĥumash, as we already learned that one fulfills his Torah obligation even without a Torah scroll according to some poskim (see Responsa Binyan Shlomo §54, Kaf Ha-ĥayim 685:35).
According to ma, one who fails to hear Parashat Zakhor on Shabbat can, be-di’avad, discharge his obligation by hearing the Torah reading on Purim, which recounts the story of Amalek’s attack (Shemot 17:8-16). mb 685:16 questions this, because that section only mentions the narrative of the war against Amalek, not the commandment to remember and eradicate it. Some authorities suggest that he should wait until later in the year when the congregation reads Parashat Ki Tetzei, which contains Parashat Zakhor at the end, and ask the reader to have in mind to absolve him of his obligation to remember Amalek. Both the reader and listener must have in mind to fulfill the mitzva (Mikra’ei Kodesh [Frank], Purim 6). In my humble opinion, however, it is best for him to read Parashat Zakhor privately, from a Torah scroll, as soon as possible, lest he forget it altogether. This way, he will fulfill his obligation according to the vast majority of poskim. Then, if he remembers, he can act scrupulously and try to fulfill the mitzva through the readings of Purim and Ki Tetzei.
The Aĥaronim dispute the reason for this mitzva. According to Keren Ora, it is in order to destroy Amalek. Therefore, once Amalek is wiped out, there is no longer any mitzva. Melekhet Shlomo maintains that the mitzva to remember Amalek will remain in effect even after it is destroyed, because of the principles of faith that it contains.
. The Rishonim disagree about whether or not mitzvot require kavana. sa 60:4 rules that mitzvot indeed require kavana. Be-di’avad, one discharges his obligation even if he did not have explicit kavana, as long as he knows that the purpose of reading Parashat Zakhor is to fulfill the mitzva of remembering Amalek, as this is considered latent kavana. One who does not know why we read Parashat Zakhor, however, does not discharge his obligation by simply hearing the passage read, according to the position that mitzvot require kavana (Ĥayei Adam, mb 60:10). One who fails to hear all the words still fulfills the mitzva, as long as he hears the main point – the injunction to remember what Amalek did to us (Halikhot Shlomo 18:1).