Jesus is both divine and human at the same time. Therefore, in the one person of Jesus are two distinct natures. This is called the hypostatic union, but, this isn't all we know about the person and work of Christ. Jesus also occupies three main offices: Prophet, Priest, and King. In other words, Jesus functions and/or has functioned in these offices. Let's take a look.
Christ as Prophet
A prophet of God is someone who reveals God, speaks for God, and communicates to people the truths that God wants them to know. Undoubtedly, Jesus did this when he came to do the will of the Father (Luke 22:42), to reveal the Father (Matt. 11:27), and to speak the things of the Father (John 8:28; 12:49).
In the Old Testament Moses said in Deut. 18:15, “The Lord your God will raise up for you a prophet like me from among you, from your countrymen, you shall listen to him." This prophecy is quoted by Peter in Acts 3:22-23 in reference to Jesus, “Moses said, ‘The Lord God shall raise up for you a prophet like me from your brethren; to Him you shall give heed in everything He says to you. 23 ‘And it shall be that every soul that does not heed that prophet shall be utterly destroyed from among the people.’" The context of Acts 3:22 is clear that it is speaking of Jesus. In Acts 3:15 it speaks of Jesus being raised from the dead. In v. 16 Jesus is the one who strengthened a certain man. Christ is mentioned in v. 18 as needing to suffer. In v. 20 Jesus is called the Christ. Verse 21 mentions how God spoke "by the mouth of his holy prophets from ancient time." Then we have v. 22 which quotes Deut. 18:15. The context is clearly about Christ.
Furthermore, Jesus refers to himself as a prophet.
- Luke 13:33, "Just at that time some Pharisees came up, saying to Him, "Go away and depart from here, for Herod wants to kill You." 32 And He said to them, "Go and tell that fox, ‘Behold, I cast out demons and perform cures today and tomorrow, and the third day I reach My goal.' 33 "Nevertheless I must journey on today and tomorrow and the next day; for it cannot be that a prophet should perish outside of Jerusalem."
- Matt. 13:57, "And they took offense at Him. But Jesus said to them, “A prophet is not without honor except in his home town, and in his own household.” 58 And He did not do many miracles there because of their unbelief.."
In Luke 13:33 Jesus refers to himself as a prophet because he knows he is about to die, but he cannot do it outside of Jerusalem. Also, in Matt. 13:57 Jesus speaks about a prophet having no honor in his home town, and that is why he did not do many miracles there. Clearly, Jesus is referring to himself as a prophet.
Christ as Priest
The priests were the ones in the Old Testament who offered sacrifices to God in order to cleanse of sin. Ultimately, all such priests were representations of Jesus who is the True Priest who offered himself as a sacrifice (Eph. 5:2; Heb. 9:26-27; 10:12) by which he cleanses us of our sin (1 John 1:7). But, Jesus is called a priest after the order of Melchizedek. “Where Jesus has entered as a forerunner for us, having become a high priest forever according to the order of Melchizedek.” (Heb. 6:20). Heb. 9:11 says, “But when Christ appeared as a high priest of the good things to come, He entered through the greater and more perfect tabernacle, not made with hands, that is to say, not of this creation." As a priest, Jesus is our mediator between God and ourselves (1 Tim. 2:5).
It could be said that both the Prophet and the priest stand between God and man. In the case of the prophet, he delivers the word of God from the top down. In the case of the priest, he delivers the sacrifices of people to God from bottom to top. So, Jesus is a prophet who delivers the word of God to us, and he is also the priest who delivers his sacrifice, on our behalf, to God the father.
Christ as King
A king is someone who has authority to rule and reign over a group of people. Jesus is just such a king. He is called the King of the Jews by the Magi (Matt. 2:2), and Jesus accepts that title in Matt. 27:11, "Now Jesus stood before the governor, and the governor questioned Him, saying, 'Are You the King of the Jews?' And Jesus said to him, 'It is as you say.'” Matt. 21:5 speaks of Jesus and says, "Behold your King is coming to you, gentle, and mounted on a donkey." Remember, Jesus is King in that he rules and judges. "And I saw heaven opened; and behold, a white horse, and He who sat upon it is called Faithful and True; and in righteousness He judges and wages war." (Rev. 19:11). The armies follow him (Rev. 19:14).
The phrase, "Kingdom of God," occurs 66 times in the NASB--most of them in the synoptic gospels. “The time is fulfilled, and the kingdom of God is at hand; repent and believe in the gospel.” (Mark 1:14). Jesus taught us to pray, "Thy Kingdom come." (Matt. 6:10). Is there a kingdom of God without a King? No. Jesus is that king: "'Are You the King of the Jews?' And Jesus said to him, 'It is as you say.'" (Matt. 27:11).
Does his three offices diminish Christ's deity?
No, they do not. Jesus is still fully divine and human even now (Col. 2:9) and presently holds the three offices mentioned above. It is simply a manifestation of the work of the person of Christ who is Prophet, Priest, and King. By the way, God is called the King in Psalm 95:3, "For the Lord is a great God, and a great King above all gods." So, if it does not diminish God's deity to be called a king, then it does not diminish or deny Christ's deity by calling him a King--or, for that matter, a Prophet and a Priest.