On the 15th of the seventh month, there is a pilgrimage festival to Jerusalem to celebrate the harvest. The Torah combines the celebration of a natural event, the harvest, with the historical memory of the Israelites living in huts (sukkot) during their sojourn in the desert (Lev. 23:33–44). Thus, Jews are commanded to celebrate the holiday by dwelling in huts for seven days. The Torah also speaks of taking from the four species and rejoicing before the Lord. The Rabbis and Karaites disputed about what those four species were. The Rabbinic list is: an etrog (citron), a willow, myrtle, and a palm frond.
For the Rabbis, the 70 animal sacrifices during the festival correspond to the 70 nations of the world. Sukkot shifts the emphasis of the holiday sequence from the individual to the universal. The prophet Zecharia associates the holiday with a universal pilgrimage to Jerusalem and the bestowal of rainfall. Sukkot was called “The Holiday” in Rabbinic literature because it had the flavor of a carnival. Among the spectacles was a water libation ceremony designed to stimulate rainfall. (All of the four species are found by or require much water.)
In the Middle Ages, it became a tradition to invite poor guests into the Sukkah (ushpizin). The mystics associated seven biblical heroes with the lower sefirot, or divine emanations, of the mystics, and wrote that by bringing people from this world into our Sukkot, we would also be inviting the divine forces from the upper world.
[Courtesy : Professor Shai Cherry]