The Midrash explains that each of the species represent a different type of Jew. The etrog (citron fruit), which has a good flavor and scent, represents the tzaddik who has both Torah wisdom and good deeds. The lulav (palm branch), which has a good flavor, but no scent, signifies a person with wisdom but no good deeds. The hadassim (myrtle branches), which have a good fragrance but no flavor, symbolize a person with good deeds but no wisdom. The aravot (willow branhes), have neither flavor nor fragrance, which signifies a person who lacks both good deeds and Torah wisdom.
We find a similar idea hidden in the ketoret (incense offering). There were eleven spices, one of which was the chelbana, which exuded an unpleasant odor. However, when combined with the other ten spices it added a tasteful pungency to the mixture. On Sukkot, we take the four species and symbolically proclaim that every Jew, no matter what level he’s at, has something to contribute to klal Yisrael.
On Hashana Rabbah, only the aravot are taken. This teaches us the absolute love Hashem has for every Jew, even the most wicked. Hashem chose us, exercising a choice unbound by logic, and he will never abandon us. Our relationship is otherworldly, something that cannot be contained in words. And just as Hashem remains loyal to us, we must love every Jew regardless of his level.
While Yom Kippur is an island of sanctity, isolated from the rest of the year, Hoshana Rabbah contains elements of the weekday. A lot of the influence of Yom Kippur has worn off by the time we get to the end of Sukkot. On Hashana Rabbah, we tell Hashem, “We want to be good, but the complexities of life make it difficult. Give us a free gift and forgive our sins.”
During the times of the beit hamikdash, the Jews would circle the altar with the aravot. This signifies that even if we fall to the lowest depths like the aravot, Hashem will lift us to the level of the altar. Large aravot were placed on the altar. The aravot were offered as a sacrifice, just as we offer our own human weaknesses to Hashem. In a sense Hoshana Rabbah goes beyond Yom Kippur. On this day it is as if Hashem tells us, “My children, you are not lost, despite your failings.”
Our sages teach us that Shemini Atzeret, the eighth day of Sukkot, is a holiday of its own. Seven signifies the cycle of nature, while eight represents something supernatural. It’s wrong for a person to think, “This is the way I am. I cannot improve.” On the contrary, we can transform ourselves because there is something extraordinary beyond nature inside each of us. Torah study, prayer, and kind deeds empower us to repent. While angels remain stagnant, people have the ability to reach unimaginable heights.
When the beit hamikdash stood, the Jews would form a human wall and encircle the altar with the four species. A wall is like an environment. There are terrible environments that must be shattered and good environments that must be built. Walking around with the lulav and etrog is akin to destroying negative barriers. Encircling the altar with the Torah is like erecting\a wall of sanctity. The Zohar writes that the female side of the satan is called yilila. This also means wailing because sadness is fundamental to evil. The opposite is also true. Therefore, the last day of the holiday is Simchat Torah. Torah signifies simcha (happiness). We rejoice with Hashem‘s love and with the privilege to build a wall of holiness and sanctity to last us through the coming year.