What does Psalm 58:9 mean?

In this passage, David points out the harm done by wicked judges and rulers (Psalm 58:1–2). He notes that they deliberately shut their ears to what is right (Psalm 58:3–5). And so, he calls on God to bring terrible, gruesome justice to these evil men (Psalm 58:6–8). Using deliberately shocking imagery, David appeals to the Lord to completely defeat such men and prevent them from doing further harm. David does not plan to take these matters into his own hands, however: these are emotional appeals for the Lord to act.

This verse emphasizes the speed with which David hopes God will act. Thorn bushes and briars typically have thin, light branches. When ignited, they are consumed very quickly. They might make good kindling (Judges 9:15), but without other fuel, they are consumed too soon to be of use. A pot set over nothing but a pile of thorns would barely feel any heat before the fire died out. The reference translated as "green or ablaze" is literally a comparison of "alive" versus "angry." This might refer to food that is raw or partly cooked—meaning the pots being cooked—or to God's ability to extinguish a fire regardless of how long it has been tended.

In another of the "imprecatory" psalms, Asaph uses the imagery of the Lord sweeping the wicked away in judgment. He writes: "How they [the prosperous, proud wicked] are destroyed in a moment, swept away utterly by terrors!" (Psalm 73:19). No one intentionally discards something of value, but a person intentionally sweeps away litter and dirt. The life that opposes God and assaults others will be swept away in judgment, because it rejected the Savior and did nothing of eternal value.