Parashat Tetzaveh devotes an entire Perek to the commandment to make the Bigdei Kehunah, the priestly garments worn by the Kohanim during the Avodah. The Torah describes this commandment as “Chukat Olam Lo ULZar’o Acharav,” “an eternal decree for Aharon and his descendants” (Shemot 28:43). Clearly, the Torah is highlighting the importance of the Bigdei Kehunah, which leads to the obvious question that many commentaries tackle: what exactly makes the Bigdei Kehunah so significant?
Ramban (28:2 s.v. LeChavod) answers this question by comparing the Bigdei Kehunah to clothes worn by royalty. He references many parallels that show that the clothing of royals is similar to the clothing of Kohanim. For example, he compares the colorful Me’il to the Ketonet Pasim that Yaakov gives to Yosef. He also compares them to the ornate clothes, as elaborately described in Megillat Esther, that Achashveirosh wears. According to Rambam, the function of the Kohanim’s uniforms, like the function of royalty’s uniforms, is to enhance the honor and prestige of the wearer.
Benno Jacob offers a different explanation, based on the story of Adam and Chava, of the siginificance of the Bigdei Kehunah. The Pasuk states (BeReishit 3:21), “VaYa’as Hashem Elokim LeAdam UeIshto Kutnot Or VaYalbisheim”, “And Hashem the Lord made for Adam and his wife garments of skin, and he clothed them.” It is strange that Hashem would make clothes for Adam and his wife, as Adam had to make every other product of civilization. Hashem does not teach him how to make fire, till the soil, or build a house. Adam uses his own intellect, which Hashem grants him, to accomplish these tasks. Benno Jacob explains that Hashem must provide clothing for man because clothing distinguishes humans from animals. Man, who is created in the image of Hashem, is not content with his nakedness, and thus he covers himself with clothing that Hashem provides. Hashem wants to distinguish between the ordinary animals and the sacred humans, so he provides the humans with clothing. Likewise, Hashem wants to distinguish between the mundane people and the sacred Kohanim who do His Avodah, and therefore He commands them to wear special clothing.
Rav Shamshon Rephael Hirsch provides another answer to this question. Rav Hirsch notes that nation of Yisrael, as opposed to the Kohanim, must provide and own the Kohanim’s garments. By wearing the clothing of the people, the Kohein becomes a servant of the people, and he performs the Avodah as a representative of the people.
This idea is expressed in the requirement of Beit Din to appoint the Kohein Gadol. The Rambam, in Hilchot Sanhedrin (5:1), states that the Sanhedrin HaGadol, the court of 71 judges, appoints the king of Israel. However, he mentions the same Halachah regarding a Kohen Gadol in Hilchot Kelei HaMikdash. Since both of these Halachot emanate from the same Tosefta in Mesechet Sanhedrin, this separation is very puzzling. The Brisker Rav explains that appointing the Kohein Gadol is not really a job of the Sanhedrin; in actuality, the entire nation must appoint the Kohein Gadol, since he represents them in front of Hashem. Perhaps for this reason Rambam does not record the Halachah regarding the Kohein Gadol in Hilchot Sanhedrin. The Kohein Gadol is appointed by the Beit Din of 71 judges because the Sanhedrin HaGadol represents the entire nation.
On Yom Kippur, the Kohein Gadol approaches Hashem as close as he possibly can; encountering Hashem’s cloud of Shechinah, he enters the Kodesh HaKadashim. Presumably, he should wear the clothes of royalty, since he is trying to get Hashem to grant forgiveness to his nation; surely the Kohein Gadol would want to appear as worthy as a good king, leading his people in service of Hashem. And yet, he specifically does not wear the golden garments of the normal Avodah. Rather, he wears plain, white linen clothes. Rashi explaisn that this is because the Michnesei Zahav will remind Hashem of Cheit HaEigel and thus strain the Mechilah process. However, there may be another reason. When wearing the eight golden Begadim, the Kohein Gadol distinguishes himself from his fellow Kohanim and from the people; he is dressed like a king. But on Yom Kippur, that distinction is useless. More so on Yom Kippur than on any other day of the year, the Kohein Gadol is the sole representative of all of Am Yisrael. The Kohein Gadol, in his simple white Begadim, breaks all barriers between fellow Jews and gets Mechilah for all of Klal Yisrael.