Leviticus 23:40 tells us:
“You should take for yourself the product of hadar trees, branches of palm trees, boughs of leafy trees and willows of the brook, and you shall rejoice before the L-rd your G-d seven days.”
Thus we have the “four species” — etrog (citron), lulav (palm frond), hadas (myrtle) and arav (willow) — and the mitzvah to wave it in all six directions (east, south, west, north, up, down) each day of the holiday, except Shabbat.
Writes Sefer Hachinuch (mitzvah 324 out of 613):
Each of these species is symbolically connected to a part of the human body — etrog the heart, lulav the backbone, myrtle the eyes and willow the lips. Accordingly, Moving Traditions has drawn a Sukkot chart: “Embodying Sukkot.”
