Here's a graphic I used in the History of Redemption walk-through. In the Old Testament God raised up special individuals to mediate Israel's relationship with God. The prophet spoke to the people on behalf of God. The priest represented the people before God. And the king ruled the people for God. These individuals were anointed with oil, and often with the Spirit.
The OT looked forward to One who would combine all the special, anointed offices. Ezekiel was both priest and prophet. David was prophet and king. But no one could combine all these offices except The Anointed One (Messiah). This was the Messianic expectation. See Deuteronomy 18, Isaiah 9, Daniel 7, and Psalm 2 and 110. Jesus perfectly reveals the Father to us, represents us before the Father, and rules us in God's righteousness.