“You shall take for yourselves on the first day the fruit of a goodly tree (ethrog), branches of palm trees (lulav), boughs of thick trees (hadassim), and willows of the brook (aravot)...”

-Emor 23:40

“R. Berechiah said in the name of R. Levi: For the merit of ‘You shall take for yourselves bayom harishon (on the first day)...’ I [G‑d] shall reveal Myself to you first... and build for you the ‘first’-i.e., the Beit Hamikdash of which it is written ‘The throne of glory, on high from the first...’ (Jeremiah 17:12), and bring to you the ‘first’-i.e., the King Moshiach of whom it is written, ‘The first unto Zion...’” (Isaiah 41:26).

-Vayikra Rabba 30:16

Chassidism explains that these four species were selected because each of them signifies the principle of unity: the leaves of the lulav are unopened and bound together; the leaves of the hadassim (myrtle-branches) must emerge from the stem “three leaves growing out of one nest”; aravot (willow-branches) are also called achvana, a word denoting brotherhood or brotherly love; and the ethrog is the “ ‘fruit of a tree that is hadar (goodly)’ read not hadar but ha-dar, i.e., a fruit which remains upon its tree from year to year” (Sukah 35a), thus compounding the climates of all four seasons of the year.

The four species indicate not only the sense of unity intrinsic to each, but also the unity of all four being taken together: the singular mitzvah of “you shall take for yourselves...” is fulfilled only when all four are taken together.

Moreover, the Midrash notes that the four species also symbolize four types of people: 1) The ethrog has taste as well as fragrance, so Israel has people who possess Torah-learning and good deeds. 2) The palm tree (lulav) has taste but not fragrance, so Israel has people who possess Torah-learning but not good deeds. 3) The hadassim have fragrance but no taste, so Israel has people who possess good deeds but not learning. 4) The aravot have no taste and no fragrance, so there are people who have neither learning nor good deeds. The Holy One, blessed be He, thus says: “Let them all be bound together as one and they will atone one for another.”

The world as a whole displays multiplicity and divisiveness, the very opposite of the Divine unity. The four species, on the other hand, signify unity, transcending worldliness and displaying submission to the Divine unity. They are themselves physical, growing in-and thus part of-the world, but they are used as a mitzvah for the Divine service. Thus they elevate physical reality and render it into an instrument for the Divine unity, revealing the concealed principle of unity inherent in G‑d’s creation.

The four species thus effect the fulfillment of the prophecies that “all shall call upon the Name of G‑d to serve Him with one consent” (Zephaniah 3:9), and “G‑d shall be King over the entire earth: in that day G‑d shall be One and His Name One” (Zechariah 14:9), which shall come about with the speedy redemption by Moshiach.