If the law of Moses was still in effect, even Jesus could not serve as a priest. But Jesus is now our High Priest, which in itself testifies to the establishment of a new order. There has been “a change in the law” (Hebrews 7:12). Moses’ law “made nothing perfect.” Its commandment about priests was “set aside” because of its “weakness and uselessness.” In contrast, Jesus as our High Priest is perfect and meets all our needs.
The former [Levitical] priests were many in number, because they were prevented by death from continuing in office, but He [Christ] holds His priesthood permanently, because He continues forever. Consequently, He is able to save to the uttermost those who draw near to God through Him, since He always lives to make intercession for them. For it was indeed fitting that we should have such a high priest, holy, innocent, unstained, separated from sinners, and exalted above the heavens. (Hebrews 7:23-26 cf. 5:1-10; 6:19-20; 7:27-28)
Notice the purpose of a high priest: People “draw near to God through” this priest. Aaron was the first of many high priests of the Old Covenant. Jesus is the first and only High Priest of the New Covenant. As the Son of Man who shared our experiences, Jesus perfectly represents fellow-humans to God. As the Son of God enthroned beside His Father, Jesus perfectly represents God to us. That is why Jesus alone can mediate between man and God and why we can approach God with complete confidence.
“There is… one Mediator. ”That fact rules out other mediators.
Since then we have a great high priest who has passed through the heavens, Jesus, the Son of God, let us hold fast our confession. For we do not have a high priest who is unable to sympathize with our weaknesses, but One who in every respect has been tempted as we are, yet without sin. Let us then with confidence draw near to the throne of grace, that we may receive mercy and find grace to help in time of need. (Hebrews 4:14-16)
For there is one God and one Mediator between God and men, the man Christ Jesus, who gave Himself as a ransom for all. (1 Timothy 2:5-6)
The term “mediator” means a “go-between”—a person who works between two people or between two parties to bring them together in agreement. Scripture is emphatic: “There is one God and one Mediator!” That singular fact rules out any other mediator or mediatrix (female mediator) such as an ancestor, a spirit, a shaman, a guru, a famous saint and even a relative of Jesus. It rules out modern priests who promote themselves as channels to God. Anyone who makes such a claim “takes this honor to himself” for he contradicts the New Covenant. He can produce no Scripture to prove that God called him. Worse, he makes himself a rival for the position that Christ alone holds. Just as the Old Covenant punished pretenders, so the Bible warns of greater punishment for crimes against the far greater New Covenant (Hebrews 2:1-3; 10:28-29).