When I was in seminary one of the professors referred to the prophets as God’s relief pitchers. They were called in to meet needs, usually when things were not going well. They came from different regions of the country and different tribes. Some like Isaiah, Jeremiah, Daniel and Ezekiel were lifelong prophets. Some like Amos and Haggai seemed to have relatively short ministries. Some were priests like Jeremiah, Ezekiel and Zechariah. Some were members of the royal family like Zephaniah and Daniel. Some were educated and urban like Isaiah and some were from rural backgrounds like Micah and Amos. They were called by God to speak for him to his people when a specific word was needed.
The King and Priests
One could be a king and a prophet like David or a prophet- priest like those mentioned above but one could not be a king priest. The kings were of the house of David and the tribe of Judah. The priests were of the house of Aaron and the tribe of Levi.
King Uzziah tried to usurp the role of the priests and was stricken with leprosy. (2 Chronicles 26:19)
A king like Josiah could challenge the priest to better fulfill their ministry. (2 Chronicles 34:8–13)
Prophets often challenged decadence in the priesthood and among the kings.
Johoiada, the High Priest, saved the Davidic monarchy from extinction. (2 Kings 11)
In Judaism, you could not be a prophet, priest, and king. Not until Jesus.
He was the king of the line of David who will reign forever.
He was a priest in order of Melchizedek, the mysterious Gentile king-priest of Jerusalem in the time of Abraham. In his priesthood Jesus was superior to the priests of the Jews who offered the same sacrifices day after day and year after year for their own sins and the sins of the people. These sacrifices, which pictured the sacrifice of Messiah, had to be repeated endlessly. Jesus, the Messiah, offered himself once, not for his own sin but for the sin of those who would put their faith in him. He was also the ultimate prophet whose ministry was not limited by class or tribe but spoke the very words of God. (John 17:13–17; Hebrews 7; 10)
On the basis of his ministry his followers can pray boldly with a clear conscience. They can have a sure hope for the future. They can be the justified who live by faith. (Hebrews 10:32–39)