What does Psalm 37:36 mean?

Although the wicked, ruthless person may succeed for a while, the Lord will judge him. He will not survive indefinitely. In the prior verse, David noted how the wicked and ruthless can seem like firmly rooted trees. He might have been thinking of his encounters with the rich Nabal (1 Samuel 25), the warrior giant Goliath (1 Samuel 17:45–51), or the jealous King Saul (1 Samuel 23:14). Or David may have been making a general statement. In any case, here David notes that those who are ungodly eventually fall. David looked for the "wicked, ruthless man" (Psalm 37:35), but couldn't find him.

Herod, who persecuted believers in the early church, was a powerful, ruthless man, but the Lord judged him dramatically in an instant. Herod had executed James, and he intended to execute Peter, but the Lord rescued Peter from prison. Later, on an appointed day in Caesarea, Herod put on his royal robes, sat on a throne, and delivered a speech. When his audience shouted, "The voice of a god, and not of a man" (Acts 12:22), "an angel of the Lord struck him down, because he did not give God the glory, and he was eaten by worms and breathed his last" (Acts 12:23).

The wicked will not execute ruthless power forever. Many will suffer the natural consequences of their sin (Proverbs 14:32). Ultimately, all those who reject God will suffer the eternal consequences of their cruelty (Revelation 20:11–15).