Messiah (Hebrew: meshiyakh) or Christ (Greek: christos) means the Anointed One. It’s a reference to an ancient initiation rite of pouring oil (along with the authoritative words of institution) which formally appoints a man to an office. In the Old Testament, there are three offices into which chosen persons are anointed by God to serve his people in his name, i.e. the prophet, the priest, and the king.
In the New Testament, we see God the Son in the form of a human servant presented as God the Father’s ultimate and consummate prophet, priest, and king all in one. He serves his people in all three capacities. Christ declares the counsel of God as prophet, intercedes in the presence of God as priest, and rules in righteousness before the face of God as king. Jesus the Son of God is the Threefold Christ.
Contemporary Evangelicalism typical speaks of the work of Christ in the categories of Lord and Savior. These dual roles certainly have their place in Scripture, especially as pairs in the Apostle Peter’s second epistle. But the Reformed tradition (drawing on the ancient church’s thinking) has found more utility in understanding the Son of God as the Messiah according to his threefold function (Latin: munus triplex).
From the Westminster Larger Catechism (contemporized by me):
Q. 42. Why was our Mediator called Christ?
A. Our Mediator was called Christ, because he was anointed with the Holy Spirit above measure, and thus he was set apart and fully equipped with all authority and ability to execute the offices of prophet, priest, and king of his church in the conditions both of his humiliation and exaltation.
Q. 43. How does Christ execute the office of a prophet?
A. Christ executes the office of a prophet in his revealing the whole will of God in all things concerning the church’s edification and salvation. He does so to the church in all ages by his Spirit and Word in diverse manners of administration.
Q. 44. How does Christ execute the office of a priest?
A. Christ executes the office of a priest in his offering up of himself once as a sacrifice without blemish to God to be reconciliation for the sins of his people. And he does so in continually making intercession for them.
Q. 45. How doth Christ execute the office of a king?
A. Christ executes the office of a king in calling a people to himself out of the world and giving them officers, laws, and censures by which he visibly governs them. He does so in bestowing saving grace upon his elect, rewarding their obedience, and correcting them for their sins. He also does so in preserving and supporting them under all their temptations and sufferings, restraining and overcoming all their enemies, and powerfully ordering all things for his own glory and their good. And he also does so in taking vengeance on the rest who do not know God and do not obey the gospel.
Or take it from Smalltown Poets back in 1997. :-p
If I indeed am misperceived by some heads of state
Hey, that’s great.
‘Cause I talk to a prophet who tells me the truth.
And I dine with a king at my home in Duluth.
Better yet, I’m in touch with a much needed friend
Who hears my confessions and pardons my sin.
But my closet’s a shrine to an old friend of mine.
Here, I talk all the time with a prophet, priest . . .
I pull out boxes and brooms; I gush like a groom.
For it’s here I commune with a prophet, priest, and king.