Psalm 7 is the second of fourteen psalms that are linked in the title to some historical event (the first is Ps. 3). We cannot know the details, but clearly David felt terribly betrayed when he was falsely charged by someone close to him who should have known better. We shall focus on the last four verses (7:15-17):

He who is pregnant with evil and conceives trouble gives birth to disillusionment.
He who digs a hole and scoops it out falls into the pit he has made.
The trouble he causes recoils on himself; his violence comes down on his own head.
I will give thanks to the LORD because of his righteousness,
and will sing praise to the name of the LORD Most High.

The colorful language makes the point tellingly. Here is someone carefully digging a pit to serve as a trap for someone else — but the digger falls in himself. The first line pictures someone “pregnant with evil” and “conceiv[ing] trouble,” but giving birth not to the trouble they intended to produce, but to (their own) disillusionment. The psalmist then expresses his conviction more straightforwardly in verse 16: “The trouble he causes recoils on himself; his violence comes down on his own head.”

David’s conviction is grounded neither in some impersonal force (“right wins out in the end”) nor in some Pollyanna-like optimism (“I’m sure it will turn out all right”), but in the righteousness of God: “I will give thanks to the LORD because of his righteousness and will sing praise to the name of the LORD Most High” (7:17). David is not blind to the injustices of the world, but he lives in a theistic universe where right will finally prevail because God is just.

If we cast our minds more broadly through the pages of Scripture (not to mention our own experience), it is easy to think of instances where the tricks and traps set by evil people recoiled on themselves before they could do any real damage. Haman hangs on the gallows he has prepared for Mordecai. But in many cases judgment falls on the perpetrator in this life, only after he or she has succeeded in doing enormous damage. David could not help but know this: he had been caught himself. He succeeded in sleeping with Bathsheba and murdering her husband Uriah before he was caught, and had to face judgment himself. Judas Iscariot’s life ended horribly, but not before he had betrayed his Master. Ahab faced prophetic wrath, but only after his wicked queen Jezebel had managed to malign Naboth and had him killed in order to steal his vineyard.

But the ultimate sanction is at the last judgment, without which there is no final justice in this universe.