“No one takes this honor upon himself; he must be called by God, just as Aaron was. So Christ also did not take upon himself the glory of becoming a high priest. But God said to him, “You are my Son; today I have become your Father” (Hebrews 5:4-5)
Jesus did not exalt himself to the position of High Priest, even though He was the only one qualified who could have easily assumed the role. Instead God appointed Him this honor. Since the introduction of the High Priest, it was God who chose who would serve at the altar. He chose Aaron and gave instruction that every high priest would be his descendant (Exodus 29:9). Aaron wasn't qualified when God chose him, having served as a slave in Egypt his entire life. Nevertheless, God chose and equipped him to intercede on Israel's behalf.
However, being human, the High Priest was never able to make intercession effectively. Both because they were subjected to the weakness of the flesh and because death prevented them from continuing in office (Hebrews 5:1-3; Hebrews 7:23). Because of this, the Levitical priesthood could only serve as a vague representation until the time of Christ. The sacrifices and intercession was only a covering for sin, it never dealt with the issue of sin. Isaiah tells us, “The LORD looked and was displeased that there was no justice. He saw that there was no one, he was appalled that there was no one to intervene; so his own arm worked salvation for him, and his own righteousness sustained him” (Isaiah 59:15-16). God saw that mankind was incapable of bringing reconciliation between God and mankind. This displeased him, so Isaiah records that God's own right arm, Jesus, worked salvation for mankind.
The amazing thing about this is Jesus is the person that God chose. He chose the very best right from the start. There was not a backup plan because the perfect plan was set into motion from the very beginning. I Peter records, "He [Jesus] was chosen before the creation of the world, but was revealed in these last times for your sake" (I Peter 1:20). Jesus' redemption of mankind was so perfect and complete, God appointed Him the honor of eternal High Priest and exalted His name far above everything in existence (Philippians 2:9-11; Hebrews 1:4). Aaron portrayed a picture of the true High Priest, helping us to understand this role, but Jesus is the embodiment of the image. The difference is that Jesus is currently making intercession for us, in heaven, in the presence of God. “Now there have been many of those priests, since death prevented them from continuing in office; but because Jesus lives forever, he has a permanent priesthood. Therefore he is able to save completely those who come to God through him, because he always lives to intercede for them” (Hebrews 7:23-25).
David prophesied about this in the Psalm, "You are my Son, today I have become your Father" (Psalm 2:7; Hebrews 1:5; Hebrews 5:5) . Jesus was always the plan. He was the perfect atonement and He is the perfect High Priest. Romans tells us that "God's gifts and his call are irrevocable" (Romans 11:29). Meaning, He does not change his mind. In fact, the position given to Jesus as High priest was given with an oath from God that it was an eternal position (Hebrews 7:21-22, 28). We can be confident in this placing our entire faith in the one who died for us, who was raised to life for us and who lives interceding at God's right hand for us. Amen!