The function of the kohanim is to connect Israel to their Father in heaven by serving in the Temple, deepening Israel’s faith and kindness, and teaching halakha. To enable the kohanim to devote themselves to this mission and to free them from the need to support themselves, the Torah commands that they be given a variety of donations and gifts. To preserve the sanctity of the kohanim, they may not become tamei by coming into contact with a corpse (except for first-degree relatives). A kohen also may not marry a divorcee or a ḥalala (the daughter of a forbidden kohen relationship, such as a kohen and a divorcee).
There is a mitzva to appoint the most outstanding kohen to serve as Kohen Gadol. The laws pertaining to him are more restrictive than those pertaining to other kohanim. He is not allowed to mourn (or become tamei) for anyone, even his parents, and he is only allowed to marry a virgin. Once appointed, he was anointed with special oil and dressed in eight vestments designated for him, as the verses state:
The priest who is exalted above his fellows, on whose head the anointing oil has been poured and who has been ordained to wear the vestments, shall not bare his head or rend his vestments. He shall not go in where there is any dead body; he shall not defile himself even for his father or mother. He shall not go outside the Sanctuary and profane the Sanctuary of his God, for upon him is the distinction of the anointing oil of his God, Mine the Lord’s. (Vayikra 21:10-12)
The Sanhedrin of seventy-one sages would decide whom to appoint as Kohen Gadol (MT, Laws of the Temple’s Vessels and Its Workers 4:12-15).
While the other kohanim wore four special vestments when they served in the Temple, the Kohen Gadol added an additional four, for a total of eight. If he performed his duties wearing only seven of them, it invalidated his avoda. Each of the vestments represents a specific idea and helped atone for sins corresponding to that idea. Thus, our Sages tell us:
The ketonet (tunic) atones for the spilling of blood; the mikhnasayim (breeches) atone for sexual sins; the mitznefet (miter) atones for arrogance; the avnet (sash) atones for sinful thoughts; the ḥoshen (breastplate) atones for injustice; the ephod (apron) atones for idolatry; the me’il (robe) atones for (public) gossip; the tzitz (gold band worn on the Kohen Gadol’s forehead) atones for brazen deeds. (Arakhin 16a).
The Kohen Gadol must be the most pious of the kohanim, one who follows in the footsteps of Aharon, the first Kohen Gadol, who “loved peace and pursued it; who loved people and drew them closer to Torah” (Avot 1:12). To emphasize his devotion to God, the words “Holy to God” were engraved on the tzitz. To express the Kohen Gadol’s feelings of love and responsibility for klal Yisrael, the names of the patriarchs and tribes of Israel were engraved on the stones of the ḥoshen, which he wore over his heart. The shoulder straps of his ephod also featured two precious stones on which were engraved the names of the tribes (MT, Laws of the Temple’s Vessels and Its Workers 9:1, 7-9). Additionally, the Kohen Gadol had to be superior to others in strength, wisdom, beauty, and wealth. If he possessed all of these except for wealth, his fellow kohanim would give him money, so that he would possess all these attributes (Yoma 18a).
If a Kohen Gadol was appointed who was neither pious nor virtuous, be-di’avad the appointment was valid, and the laws pertaining to the Kohen Gadol applied to him. However, it should be obvious that the more righteous the Kohen Gadol was, the more successful he would be in his work to draw Israel closer to their heavenly Father.
The Sages tell us that during the 410 years of the First Temple, eighteen Kohanim Gedolim served. Most of them were righteous, and accordingly were blessed with longevity. In contrast, during the 420 years of the Second Temple, there were over three hundred Kohanim Gedolim. Three of them were righteous and served for extended periods. Almost all the rest were not righteous. They bought their positions from the ruling powers, and their lives were cut short. Thus, we read, “The fear of the Lord prolongs life, while the years of the wicked will be shortened (Mishlei 10:27)” (Yoma 9a).
The shortcomings of the High Priests during the Second Temple period was harmful to the purity and atonement that Israel could attain on Yom Kippur. Ultimately, the Temple was destroyed, and the Jews went into a prolonged exile.