Another explanation: "The fruit of a beautiful tree" - these are [referring to] Israel. Just like this citron (etrog), which has taste and has smell, so too Israel has among them people that have Torah and have good deeds. "The branches of a date palm" - these are [referring to] Israel. Just like this date, which has taste and has no smell, so too Israel has among them those that have Torah but do not have good deeds. "And a branch of a braided tree (a myrtle)" - these are [referring to] Israel. Just like this myrtle, which has smell and has no taste, so too Israel has among them those that have good deeds but do not have Torah. "And brook willows" - these are [referring to] Israel. Just like this willow, which has no smell and has no taste, so too Israel has among them people that have no Torah and have no good deeds. And what does the Holy One, blessed be He, do to them? To destroy them is impossible, but rather the Holy One, blessed be He, said "bind them all together [into] one grouping and these will atone for those." And if you will have done that, I will be elevated at that time. This is [the meaning of] what is written (Amos 9:6), "He Who built the upper chambers in the heavens" (indicating his elevation). And when is He elevated? When they make one grouping, as it is stated (Ibid.), "and established His grouping on the earth." Hence Moshe warned Israel, "And you shall take for yourselves on the first day."
Another explanation: "The fruit of a beautiful tree (ets hadar)" - this is [referring to] the Holy One, blessed be He, as it is written about Him (Psalms 104:1), "You were dressed in splendor and beauty (hadar)." "The branches of a date palm" - this is [referring to] the Holy One, blessed be He, as it is written about Him (Psalms 92:13), "The righteous One flourishes like a date palm." "And a branch of a braided tree (a myrtle)" - this is [referring to] the Holy One, blessed be He, as it is written (Zechariah 1:8), "and He is standing among the myrtles." "And brook willows (arvei nachal)" - this is [referring to] the Holy One, blessed be He, as it is written about Him (Psalms 68:5), "praise the One that rides in the skies (aravot), with His name of the Lord."
Another explanation: "The fruit of a beautiful tree (ets hadar)" - this is [referring to] our father, Avraham, who the Holy One, blessed be He, graced (hider) with a good old age, as it is stated (Genesis 24:1), "And Avraham was old, had come along in days;" and it is written (Leviticus 19:32), "and you shall grace (hadarta) the old." "The branches (kappot) of a date palm" - this is [referring to] Yitschak, who was bound (kafut which is spelled with the same letters as kappot) and tied up on top of the altar. "And a branch of a braided tree (a myrtle)" - this is [referring to] Yakov. Just like this myrtle bustles with leaves, so too was Yakov bustling with children. "And brook willows" - this is [referring to] Yosef. Just like this willow gets withered before these three [other] species, so too did Yosef die before his brothers. Another explanation: "The fruit of a beautiful tree (ets hadar)" - this is [referring to] Sarah, who the Holy One, blessed be He, graced (hider) with a good old age, as it is stated (Genesis 18:11), "And Avraham and Sarah were old." "The branches of a date palm" - this is [referring to] Rivka. Just like this date palm, it has food and it has thorns, so too Rivkah brought up a righteous one and an evildoer. "And a branch of a braided tree (a myrtle)" - this is [referring to] Leah. Just like this myrtle bustles with leaves, so too was Leah bustling with children. "And brook willows" - this is [referring to] Rachel. Just like this willow gets withered before these three [other] species, so too did Rachel die before her sister.
Another explanation: "The fruit of a beautiful tree (ets hadar)" - this is [referring to] the Great Sanhedrins (high courts) of Israel, who the Holy One, blessed be He, graced (hider) with a good old age, as it is stated (Leviticus 19:32), "And you shall get up in front of a venerable one." "The branches (kappot) of a date palm" - this is [referring to] the Torah scholars who force (kofin) themselves to learn one from the other. "And a branch of a braided tree (a myrtle)" - this is [referring to] the three rows of students who would sit in front of them (since three myrtle branches are customarily waved). "And brook willows" - this is [referring to] the two judges' scribes who would stand in front of them and write down the words of those who would render innocent and the words of those who would render guilty (since two willow branches are customarily waved).
The Symbolism of the Four Species, Rav Meir Shpiegelman
The four species we take on Sukkot symbolize four different forms in which water appears in the world. The aravot, or "brook willows," symbolize the water in brooks and streams. The lulav is taken from the palm tree, which grows near fountains of water. The etrog, as Chazal describe (Sukka 35a; Kiddushin 3a), "grows on any water," even through irrigation, and does not depend on proximity to a natural water source. Finally, the hadasim depend entirely on rainwater.
In Eretz Yisrael, water serves a dual purpose. Beyond its standard function as a liquid critical for the existence of all living things, it also symbolizes God's close supervision over the Land of Israel:
"For the land that you are about to enter and possess is not like the land of Egypt from which you have come, where you sow your seed and water it by your foot, like a vegetable garden. But the land you are about to cross into and possess is a land of hills and valleys – it drinks water from the rain of the heavens. It is a land which the Lord your God looks after, on which the Lord your God always keeps His eye, from year's beginning to year's end." (Devarim 11:10-12)
The festival of Sukkot relates to the Almighty's providence over Am Yisrael when they left Egypt and then entered the land. We therefore celebrate this festival by taking the four species, which symbolize divine providence as manifest through water.
The Arba'ah Minim, Alan Lucas (Rabbinical Assembly)
In some ways, the mitzvah of the lulav and etrog presents a bit of a challenge to moderns accustomed to rituals that are transparent in their meaning and easily decipherable. Still, one of the dangers in contemporary Judaism is precisely that we have become overly cerebral in our approach to religion. After the intense High Holiday period of prayer and introspective thought, Sukkot appeals to our senses. We build the sukkah with our hands, and we smell the four species and shake them back and forth as a sign of our exuberant sense of thanksgiving to God for all that we have in this world. Judaism makes demands both on the intellect and the spirit, both on the brain and on the heart, and Sukkot is a vibrant reminder of this lesson.