John Calvin Commentary Psalms 37:20

"But the wicked shall perish, And the enemies of Jehovah shall be as the fat of lambs: They shall consume; In smoke shall they consume away." — Psalms 37:20 (ASV)

For the wicked shall perish. The causal particle כי (ki), which is here translated for, might also be rendered adversatively as but or although, unless, perhaps, some would prefer to interpret the sentence as having much greater significance.

But the preferable interpretation is that there is a contrast here between the subjects being discussed: namely, that the righteous are satisfied in the time of famine, whereas the ungodly shall perish in the midst of their affluence. For, while they trust in their abundance, God brings them to nothing by secret and hidden means.

In calling them the enemies of Jehovah, he teaches us that they are justly overwhelmed by his vengeance, which they bring upon themselves by their own wickedness. When he says that they shall be consumed as the excellency of lambs, this is understood by some to refer to their fat.

But as יכר (yakar) signifies excellency, as I have said elsewhere, I have no doubt that this expression denotes the very best of lambs, and those of extraordinary fatness; and this is very suitable to the contrast stated here. We learn from this what another prophet also teaches: that the ungodly are fattened for the day of slaughter, so that the more sumptuously they have lived, the more suddenly shall their destruction come upon them.

To be consumed into smoke has the same meaning as to vanish away quickly; as if to say, there is no stability or substance in them. Those who understand the term יקר (yakar) to mean fat, explain this last clause in this sense: that the wicked are consumed into smoke as fat melts or wastes away. But the reader will see that the first interpretation is better.