David appeals to the justice of the Lord. His prayer is from the heart. Note the repeat: arise,
lift yourself up,
awake.
God never sleeps nor slumbers (Psalm 121:4). Under the law, the Lord must bring the enemy to a stop. This is what he is known for. See also Psalm 94:15 for justice will return to the righteous.
For this, he can engage the earthly rulers. And so this matter becomes something of world importance. They seem like a jury in a court, in service of the Lord. But the Lord God is the highest adjudicator in the court. We can assume that the poet is a king.
6 Arise, O LORD, in your anger; lift yourself up against the fury of my enemies; awake for me; you have appointed a judgment.