“So also Christ did not glorify Himself to become High Priest, but it was He who said to Him: ‘You are My Son, Today I have begotten You'” (Hebrews 5:5).
As mentioned earlier, there were no legitimately self-appointed leaders among the members of the Old Testament priesthood. Instead, the Biblical priesthood was an institution that was established by God, with leaders who were ordained for their positions. This was true of the Levitical High Priest but it is also true of Jesus as well…
“Christ did not call Himself to the office of High Priest; the Father called Him to the honor. Both Psa. 2:7 and 110:4 are cited to prove this fact. Psalm 2:7 is also quoted in 1:5 to prove Christ’s superiority to the angels, and now the writer uses the quote to prove Jesus’ special relationship with God the Father. The quote from Ps. 110:4 highlights the eternal nature of Jesus’ priesthood. He will be Mediator between God and us forever.” (1)
Another scholar adds…
“The writer is careful to let the reader see that it was no personal ambition on Messiah’s part that resulted in His becoming a high priest, but rather the fact that God called Him to that position, and that the call to priesthood was based upon the fact that the Messiah was God s Son.” (2)
Since a High Priest of the Biblical era was chosen from among the descendants of Aaron, the Old Testament patriarch, the idea that “Christ did not glorify Himself to become High Priest” would have been difficult for many first-century Jewish audiences to accept. As another commentator explains: “It was easy to see why the priesthood of Jesus would be difficult for early Jewish Christians to grasp. He was not from the lineage of Aaron. He claimed nor practiced no special ministry in the temple; He confronted the religious structure instead of joining it.” (3)
Hebrews 5:5 addresses that objection by noting that Jesus’ priestly calling stems from His unique position as the Son of God (see Matthew 3:16-17). In addition, Jesus fulfils another qualification for the office of a High Priest that our author has previously established: He is a human being with a compassionate nature who serves an intermediary in representing God to others and others before God.
We’ll consider these aspects of Jesus’ priestly ministry shortly, but first we’ll address a potentially troublesome question: what does this passage mean when it says regarding Christ, “…Today I have begotten You”?
(1) Earl D. Radmacher, Ronald Barclay Allen, and H. Wayne House, Nelson’s New Illustrated Bible Commentary (Nashville: T. Nelson Publishers, 1999), 1642.
(2) Kenneth S. Wuest, Word Studies in the Greek New Testament (Hebrews 5:5) Copyright © 1942-55 by Wm. B. Eerdmans Publishing Co.
(3) Guzik, Dave, Hebrews 5 – Jesus, A Priest Forever https://enduringword.com/bible-commentary/hebrews-5/