A major theme of Succot is the idea of אחדות, unity. The intention of the sacrifices was to bring unity to the whole world. Seventy bulls were offered in total during the holiday, corresponding to the seventy nations. The idea of אחדות is represented primarily by the taking of the ארבעה מינים, the four species. Each specie is supposed to represent a different type of Jew. The Etrog that possesses the good taste and good smell is symbolic of the Jew with good thoughts and good actions. The willow has no taste and no smell which represents the lowest level Jew. Nevertheless, we take all four species to unite all Jews of all backgrounds. As a people, we are strongest when we are united. All of our problems come through factionalizing, and separation. Our Rosh Hashana and Yom Kippur prayers came with the words, ויעשו כולם אגודה אחת, that we should all become one unit with a complete heart in serving Hashem.