Our study of Hebrews 7 requires us to walk through some deep theological teaching on the priesthood of Christ and the law of God that is based on the figure of Melchizedek, who is fairly obscure to many people because the Old Testament says very little about him. Yet, we should not let the relative obscurity of Melchizedek blind us to the immensely comforting truths wrapped up in Christ’s Melchizedekian priesthood. Today’s passage, in fact, takes the truth of Christ’s priesthood as a great comfort to us.
Again quoting from Psalm 110, the author of Hebrews notes that Christ’s priesthood, unlike the priesthood of the Levites, was secured by an oath (Heb. 7:20–21). In light of the fuller explanation in the teaching of Jesus (Matt. 22:41–46), we understand that Psalm 110 gives us a window into the interchange between God the Father and God the Son incarnate in which the Father swears an oath to make the incarnate Son a priest forever in Melchizedek’s order. Of course, this was never done with the Levitical priesthood, which was given by fiat but not established forever by a divine vow. One thing to note here is that the lack of an oath means, implicitly, that the Levitical priesthood and thus the Mosaic religious system were never meant to be in place forever. God was never committed to them as He is to the order of Christ’s priesthood.
Second, in light of Hebrews 6:13–20, God’s swearing an oath to make Jesus a priest forever greatly comforts us. It convinces us that our Creator is committed to the mediatorial work of Jesus and to none other. We never have to fear that God will change His mind about Christ’s priesthood or that the work of Jesus will prove inadequate to accomplish the purposes God has for it. The Lord, as it were, put His own honor on the line when He swore to establish Christ as the eternal, perfectly effectual priest in the order of Melchizedek. And since God will not sacrifice His own honor (Isa. 42:8), Jesus must remain our High Priest forever and really will save all those who have been given to Him by the Father. John Owen comments, “Christ’s being made a priest forever by the oath of God, is a solid foundation of peace and consolation to the church.”
Finally, the unchanging and unfailing commitment of God to the covenant in Christ, as seen in the divine oath, proves that the new covenant is better than the old (7:22). It will last forever, so there is no good reason to abandon Jesus.