In Hebrews 5:1–4, the author describes in detail the office of high priest. This is done so that his readers will make their own implicit comparisons between the high priests of the old covenant and Christ, the great High Priest of the new covenant. In 5:5–10, the author tells us explicitly how Christ was appointed to be High Priest, and he briefly describes the offerings that Jesus made unto the Father.
In 5:5 we are told that Christ did not exalt Himself into the high priestly office but rather was appointed by the One who calls Him Son. This one is, of course, God the Father. Christ did not seek out the priestly office for Himself but rather agreed to take it upon Himself when the three persons of the Trinity made a covenant among themselves to redeem humanity. The idea that the Son was appointed by the Father is well attested in the gospel of John. Throughout John’s account, we see the Son seeking glory for His Father and not for Himself (John 7:18; 14:13). In John, the Son declares that He only reveals to the people what had been given to Him by the Father (John 5:19–24). The Son came to do what His Father sent Him to do, and the Father sent Christ to be the High Priest of His people (Heb. 5:5).
In verse 6, the author applies Psalm 110 to Christ. This Psalm prophecied that the Messiah will belong to the priestly order of Melchizedek. You will remember that Melchizedek was king of Salem and priest of the Most High God. The Hebrew Scriptures tell his story in Gen. 14:17–20. We will see the full significance of Christ belonging to the priestly order of Melchizedek in Hebrews 7. Here we will simply note that Melchizedek was both a king and a high priest and thus is an excellent type of Christ who is also King and Priest.
The quotes about Sonship and priesthood in these two verses tell us something very important about redemption. Both open with the same words “you are ...,” and both are from the book of Psalms. These facts, combined with their juxtaposition in the epistle, tell us that in redemption, Sonship and Priesthood are united. For redemption to take place in God’s economy, the Son has to be the High Priest, and the High Priest has to be the Son. To be sure, God was not required to save us. But once God decided to purchase our redemption, He could only accomplish it by appointing His Son to be the great High Priest.
God the Son willingly submitted to God the Father in order to achieve our redemption. Though we will never have to do the work of the Son, we are often called to submit to those within the church, the family, and the workplace in order to advance the kingdom. Ask God to help you submit where submission is mandated by Scripture.