“Christ is the same yesterday, today, and forever. He does not just perform prophetic, priestly, and kingly activities but is Himself, in His whole person, prophet, priest, and king. And everything He is, says, and does manifests that threefold dignity.
Granted, in the one activity it is more His prophetic office that is evident to us, and in another it is His priestly or His kingly office that stands out; and it is also true that His prophetic office comes to the fore more in the days of the Old Testament and during His days of traveling around on earth, His priestly office more in His suffering and death, His kingly office more in His state of exaltation.
But actually He bears all three offices at the same time and consistently exercises all three at once before and after His incarnation, in both the state of humiliation and that of exaltation…
While it is not possible to separate them, the distinction between them is most certainly there. To be a mediator, to be a complete savior, He had to be appointed by the Father to all three and equipped by the Spirit for all three offices.
The truth is that the idea of humanness already encompasses within itself this threefold dignity and activity. Human beings have a head to know, a heart to give themselves, a hand to govern and to lead; correspondingly, they were in the beginning equipped by God with knowledge and understanding, with righteousness and holiness, with dominion and glory.
The sin that corrupted human beings infected all their capacities and consisted not only in ignorance, folly, error, lies, blindness, darkness but also in unrighteousness, guilt, moral degradation, and further in misery, death, and ruin.
Therefore Christ, both as the Son and as the image of God, for Himself and also as our mediator and savior, had to bear all three offices. He had to be a prophet to know and disclose the truth of God; a priest, to devote Himself to God and, in our place, to offer Himself up to God; a king, to govern and protect us according to God’s will.
To teach, to reconcile, and to lead; to instruct, to acquire, and to supply salvation; wisdom, righteousness, and redemption; truth, love, and power– all three are essential to the completeness of our salvation.
In Christ’s God-to-humanity relation, He is a prophet; in His humanity-to-God relation He is a priest; in His headship over all humanity He is a king. Rationalism acknowledges only His prophetic office; mysticism only His priestly office; millennialism only His royal office.
But Scripture, consistently and simultaneously attributing all three offices to Him, describes Him as our chief prophet, our only high priest, and our eternal king. Though a king, He rules not by the sword but by His Word and Spirit.
He is a prophet, but His word is power and really happens. He is a priest but lives by dying, conquers by suffering, and is all-powerful by His love. He is always all these things in conjunction, never the one without the other: mighty in speech and action as a king and full of grace and truth in His royal rule.”
–Herman Bavinck, Reformed Dogmatics, (Grand Rapids: Baker Academic, 2006), 3:367-368.