What does verse 6 in the psalm mean by the King on the holy hill of Zion?
Verse 6 pictures the King—the Messiah—set upon Zion's holy hill, meaning the Kingdom is established on earth immediately after the Tribulation. It follows the wrath and vexation of verse 5 with no gap, showing the Old Testament program: rejection, Tribulation, then the King's reign.
Les explains that verse 5 is the Tribulation, and verse 6 immediately follows with no indication of any gap. Verse 6 speaks of the King setting upon the holy hill of Zion—the Kingdom. Just as the nations, Rome and Jew together, conspired, crucified, and rejected Christ, God called Him back to heaven (Psalms 110:1), to sit at His right hand until His enemies are made His footstool. That is followed by the wrath and vexation in verse 5, then the Kingdom in verse 6. Les points out the order: the Old Testament program expected these events to take place one right after the other, with no room in Psalms for 2,000 years.