Do not worry about the wicked (v. 1-2). Fret and envy seem like two different ideas in English, although they are used parallel here in Psalm 37. To “fret” in Hebrew (hitpael of חרה) as the sense of burning with anger, a “passionate intensity, a consuming indignation” (Ross, 805, n. 28). Maybe a contemporary English equivalent would be “don’t get steamed about what the wicked are doing.” Beth Tanner (NICOT, 348) suggests, “Do not let your anger burn concerning the evil ones.”
The main reason the wise person does not need to worry about the wicked is their fate will soon overtake them. The whole Psalm will repeat the coming judgment of the wicked, here they are described as like the green grass. Considering a Middle Eastern background for the Psalm, the wicked are like the beautiful green grass that quickly grows after the spring rains, but as soon as the rains stop and the heart of summer comes, they fade away. Recall again Psalm 1, the wicked are like bushes in the desert, far from springs of living water. It is a simple natural fact people who appear to prosper in their wickedness will fade away in the heat of the coming judgment.
Rather than fret, the wise will trust in the Lord (v. 3-6). To “trust in the Lord” in this context means to trust God to sort out the difficulties of life. He will judge these wicked people who appear to be prosperous at the proper time.” Beyond trusting the Lord to sort out the unfairness of life, the righteous will delight themselves in the Lord. The verb translated “delight” (ענג, hitpael imperative) can have the sense of “pamper” or “refresh,” probably “take pleasure” in this context.
There are some things we tend to relish, whether a nice cup of coffee with a piece of fresh apple pie (you fill in your own personal favorite, this one is mine). These are not things we get all the time, so when he get them we take a great deal of pleasure in eating them slowly, savoring every bite. Perhaps there is a sense of jealous pleasure here as well, since if we really like the dessert we do not want to share even a bite with anyone else.
I think this is not the way most people think of their opportunity for communion with the Lord. Most Christians are not jealous of their time at church, or protective of their time in the Bible. There are few people I know who jealously guard their time at church, most try to find ways to avoid worship in the interest of “family time.”
Yet Psalm 37 says the righteous delight in the Lord because they are ultimately committed to him.