What is the biblical role of the high priest?

TL;DR:

The high priests made atonement for the people each year on the Day of Atonement. The biblical role of the high priest points to Jesus, our ultimate High Priest by whom we have access to God’s presence and the forgiveness of sins.

what does the bible say?

The high priest in the Old Testament was the chief spiritual leader of Israel, responsible for mediating between God and the people through sacrifices and intercession, particularly on the Day of Atonement when he entered the Holy of Holies to make atonement for the nation's sins (Leviticus 16:29-34). Chosen from Aaron's lineage, he performed duties that symbolized holiness and pointed to the ultimate High Priest, Jesus Christ, who fulfilled the role perfectly (Hebrews 4:14-16). High priests were held to a higher standard of holiness among the Levitical priests. For example, they could not touch dead bodies except for close relatives, could not have specific physical deformities, and could marry only Israelite virgins. People trusted them for seeking God's will, and they wore elaborate garments including the Urim and Thummim, symbolizing their role as intercessors for Israel. Their main duty was to perform sacrifices, especially on the Day of Atonement, to cleanse the sins of the people before God. Jesus is the ultimate High Priest whose sacrifice grants direct access to God, rendering the old sacrificial system unnecessary. Through Jesus, believers have access to God's presence without the need for other intermediaries, relying on His grace received through faith.

from the old testament

Priests came from Aaron’s line, and from the priestly line, one priest was chosen as the high priest at a time. The high priests lived much like the regular priests, only they had a few special responsibilities that set them apart. They were also held to a higher standard of holiness than the rest of the priests. The high priests were forbidden from coming into contact with any dead body including those of close relatives, they were not to shave their heads or cut their beards, they could only marry Israelite virgins, and they could not perform their priestly duties if they had any physical deformities (Leviticus 21). It is not that being dead or having deformities was a sin, but high priests had higher standards to follow since they were the mediators for the people to God.
The people would often go to the High Priest when they were seeking the will of God (Exodus 28:30; Numbers 27:21; 1 Samuel 23:9-12).
The High Priests wore special garments made of gold, purple, blue, and scarlet. These garments consisted of a breastpiece, an ephod, a robe, a coat, a turban, and a sash (Exodus 28:4-5). One particular part of their special garments was the Urim and the Thummim (Exodus 28:30; Leviticus 8:8).
The High Priest wore a breastpiece of judgment adorned with twelve precious stones, each inscribed with the name of one of the twelve tribes of Israel, symbolizing his role in bearing the people before God in intercession and judgment (Exodus 28:17-21, 28:29-30). The high priest was to wear on his breastpiece and his shoulders: "So Aaron shall bear the names of the sons of Israel in the breastpiece of judgment on his heart, when he goes into the Holy Place, to bring them to regular remembrance before the LORD. And in the breastpiece of judgment you shall put the Urim and the Thummim, and they shall be on Aaron's heart, when he goes in before the LORD. Thus Aaron shall bear the judgment of the people of Israel on his heart before the LORD regularly" (Exodus 28:29–30).
The high priest's main duty was to make sacrifices for the peoples' sins once a year on the Day of Atonement (Leviticus 16). Because God is wholly good and pure, He cannot dwell with impurity, so the place where God's presence dwelt on the mercy seat was separated from the rest of the temple by a large, heavy drape. On the Day of Atonement the high priest would ceremonially cleanse himself before entering the Holy of Holies. He would take the blood of the sacrifice and sprinkle it on the mercy seat to make atonement for the sins of the congregation.

from the new testament

John 11:49–52 possibly indicates that the high priests often had the gift of prophecy.

implications for today

Jesus is the ultimate High Priest (Hebrews 2:17; 3:1; 4:14—5:10; 6:20; 7:11—8:13; 10:12). Jesus was the perfect sacrifice that paid the price once and for all for our sins. When He died, the veil in the Holy of Holies tore, allowing people to have direct access to God when they place their faith in Jesus. Jesus is now our "better hope . . . through which we draw near to God" (Hebrews 7:19). Because our sin was imputed to Christ and His righteousness is imputed to us (2 Corinthians 5:21) we now have access to God's presence without an animal sacrifice or ceremonial cleansing. Jesus was the once-for-all sacrifice, fulfilling the Old Testament sacrificial system and making it no longer necessary. Hebrews 10:19–23 explains, "we have confidence to enter the holy places by the blood of Jesus, by the new and living way that he opened for us through the curtain, that is, through his flesh, and since we have a great priest over the house of God, let us draw near with a true heart in full assurance of faith, with our hearts sprinkled clean from an evil conscience and our bodies washed with pure water. Let us hold fast the confession of our hope without wavering, for he who promised is faithful." Jesus Christ now acts as the sole mediator between man and God (1 Timothy 2:5). We do not have to go to any religious leader for access to God, but instead rely on God's grace received through faith in Jesus (Ephesians 2:8–10).

understand

High priests were descendants of Aaron, and one high priest from the Levitical line served at a time.
High priests were priests who had unique responsibilities and high standards of holiness and purity.
The main duty of the high priest was to make sacrifices, particularly on the Day of Atonement, for the sins of the people.

reflect

How does understanding the biblical role of the high priest deepen your appreciation for Jesus as our ultimate High Priest?
In what ways do you think the responsibilities and standards of the high priests reflect God's holiness and the seriousness of sin?
Reflect on how the concept of atonement through sacrifices performed by the high priests in the Old Testament points to the sacrificial work of Jesus Christ on the cross.

engage

How does Jesus fulfill the role of the high priest described in the Old Testament, particularly regarding atonement and mediation?
What is the significance of the veil in the temple tearing upon Jesus' death and its implications for our access to God's presence?
How does the understanding of Jesus as our ultimate High Priest impact our approach to God and our understanding of forgiveness and salvation?