But the wicked will perish:
The LORD's enemies will be like the beauty of the fields,
they will vanish—vanish like smoke.
I find this verse much easier to understand in the context of verse 19. We’ve just been given assurance that in times of trial, the righteous will be satisfied; the righteous will have at least “just enough.” But, the wicked will perish. To our 21st century ears this seems so harsh, and to others, it points to the “schizophrenic” nature of Christianity: a loving and just God willing to punish so harshly.
I see it differently. The universe has an order. As creator of that order, God communicates truths about it for us to understand. It can be difficult to follow God and rely on Him in times of prosperity. The Hebrew Bible constantly reminds us to “remember” how God brought us from captivity and how easy it is to forget our God when we’re living in the land of “milk and honey.”
When times are good, it is hard to follow God, and many of us choose not to. We were just promised however that those who follow God in the good times will be preserved in the bad. We’ve learned to rely on God with food on the table, so now we can easily rely on his provision when the cupboard is bare. He will sustain us. But the wicked, we’ve been living for ourselves and exploiting the fat of the land. I’ve gotten by on my own, but now, there are times of trouble, and I’m not good enough to make it on my own. I am a sheep without a shepherd. So while the righteous continue to live on the sustenance of God, I perish in the famine thinking that I can somehow make it on my own.