There is a famous teaching of our Rabbis (Vayikra Rabbah 30:12) that there are four types of Jews. There are some Jews compared to an etrog, which has a good taste and a good smell, and these Jews possess both Torah learning and mitzvah observance. The Lulav (palm branch) has a good taste but no smell representing the Jews who learn Torah but do not observe the mitzvot. And there are some Jews like the Hadas (myrtle) which has a good smell but no taste. These Jews fulfill the mitzvot but do not learn Torah. And then there is the Aravah (willow) which has no smell and no taste like the Jews without Torah or mitzvot. The midrash concludes that these groups join together – when we hold the Four Species together - and one atones for the other. The Ramchal explained in his book "Mesilat Yesharim" (end of chap. 19) that Hashem does not want Jews to separate from one another. One group atones for the other. Thus, if you are an Etrog you should not place yourself above others and say that they are no good. You are an Etrog – full of Torah and mitzvot – for all of the Nation of Israel.
There is a story found in the Beit Yosef (Orach Chaim 651) that Rabbi Menachem Rakanti once had a dream in which he saw Hashem's four-letter name written with the first three letters together and then the last letter of its own. He woke up quite bothered and did not understand the meaning of the dream. In the morning, he saw that there was a guest who held the Lulav, Hadas and Aravah in one hand and the Etrog in the other hand and did not join them together. He then understood that according to the mystical teaching the Four Species correspond to the four letters of Hashem's Name. One who separates the Four Species, separates the letters of Hashem's Name. We can go even further to say that one who causes discord and fragmentation among the Nation of Israel also causes a separation among the letters of Hashem's Name. This idea is found in the teachings of Rabbi David Tabil of Minsk, the author of "Nachalat David" (Beit David, darash 6 quoted in Olat Re'eiyah vol. 2, p. 468). This is also written in the midrash about the Four Species which we mentioned that Hashem says: If you become one united group, I will be elevated. Everything is dependent on the Nation of Israel uniting.
We will not cease speaking about the importance of the unity of the Nation of Israel. Our Rabbi, Ha-Rav Tzvi Yehudah would repeat himself over and over regarding important matters.
People occasionally say: The time has arrived to unite the camp. Baruch Hashem, we have finally reached an ideal upon which everyone can agree. Only one small detail remains: Who is this camp? There are obviously many camps and each marches with its large flag and small trumpets. And each camp thinks it possesses the entire truth, and the other camps are members of a different religion. Since everyone is suggesting a camp, I will also give my suggestion. The camp I suggest is the entire Nation of Israel. This is the true camp. Do not be confused into thinking that you have the entire truth. This is contained within the entire Nation of Israel and everyone is needed. It does not help that the Etrog is better than the other species, since you cannot fulfill the mitzvah with four Etrogim. You need all four species. The Master of the Universe spread all of the talents among the entire Nation. Therefore, if you see someone who looks empty, perhaps he is not. After all, our Sages say (Sanhedrin 37a) that every the empty ones in the Nation of Israel are full of mitzvot like a pomegranate.