The Torah in Parashat Emor (Vayikra 23:40) introduces the Misva of “Arba Minim” – to shake the four species on Sukkot. It commands that we should take on the first day of Sukkot a “Peri Etz Hadar” – referring to the Etrog; “Kapot Temarim” – referring to a Lulab; “Anaf Etz Abot” – referring to Hadasim; and “Arbeh Nahal”- referring to Arabot. (Although the Torah writes “Kapot Temarim,” in the plural form, nevertheless, the word “Kapot” is written without a “Vav,” implying that it should be read as “Kapat,” in the singular form. The Sages thus understood that we take just a single palm branch.) In explaining the reason behind this Misva, the Sefer Ha’hinuch reiterates his principle that people’s minds and feelings are impacted by the actions they perform. The time of year when Sukkot is observed – early autumn – is the time of the harvest, when farmers are collecting their produce and bringing it into their homes and warehouses. This is a time of joy and festivity, as the farmers literally reap the fruit of their labor. G-d wanted us to channel this joy toward Him, to transform the joy over material prosperity into an experience of spiritual joy. He therefore commanded us to observe a festive holiday during this time, and to take these four species, an action which, the Sefer Ha’hinuch writes, evokes feelings of joy. Looking at these plants, and holding them, enhances one’s feelings of jubilation, and so G-d commanded us to take these species as part of our celebration of Sukkot. On other holidays, the Sefer Ha’hinuch writes, we do not need these plants to evoke feelings of joy, because on Pesach we already have the Masa, Marror, and other festive components, and on Shabuot we celebrate the Torah, and thus we do not need any external feature to arouse our joy. The Sefer Ha’hinuch adds in this context the Sages’ famous teaching that the four species correspond to four parts of the body. The Etrog resembles the heart, the source of the intellect, and we thus take an Etrog to signify the need to devote our minds and thoughts to the Almighty. The Lulab resembles the spine, and it thus represents the subjugation of the body to the service of the Creator. The leaves of the Hadasim resemble the eyes, symbolizing the need to exercise care not to be drawn after that which we see. Finally, the leaves of the Arabot are shaped like the mouth, and thus represent the vital importance of guarding our mouths against forbidden speech. Each of the four species is indispensable for the fulfillment of the Misva. This means that if a person has only three of the four species, he cannot fulfill the Misva; there is no value in taking the three species in such a case. This Misva applies only to males; as it is a “Misvat Aseh She’ha’zman Gerama” (an affirmative command that is confined to a specific time-frame), it is not obligatory upon women. This Misva applies in all times, and, on the first day of Sukkot, in all places. Torah law requires taking the four species everywhere on the first day of Sukkot, but only in the Bet Ha’mikdash on the subsequent six days. The Sages, however, enacted that the four species should be taken everywhere even on the last six days. According to some opinions, including that of the Rambam, the Torah obligation to take the four species on all seven days applies not only in the Bet Ha’mikdash itself, but throughout the city of Jerusalem. For this reason, there are those who make a point of going to Israel for Sukkot so they can take the four species in the Old City of Jerusalem on each day of the holiday, and thus have the privilege of fulfilling the Misva on the level of Torah law each day. Others, however, understood that the Torah obligation applies only in the Bet Ha’mikdash, and not elsewhere in Jerusalem.