Augustine of Hippo

What should you do then? "Trust in the Lord" [Psalm 37:3]. For they too trust, but not "in the Lord." Their hope is perishable. Their hope is short-lived, frail, fleeting, transitory, baseless. "Trust thou in the Lord." "Behold," you say, "I do trust; what am I to do?" "And do good." Do not do that evil which you behold in those men, who are prosperous in wickedness. "Do good, and dwell in the land." Lest haply you should be doing good without "dwelling in the land." For it is the Church that is the Lord's land. …

Exposition on Psalm 37 ↗

Ambrose of Milan

Therefore the Prophet rightly says: Hope in the Lord, and do good; and you shall inhabit the land, and shall be fed with its riches. What is the land that he advises to inhabit, if not your soul, which you should cultivate well, frequently plowing it with spiritual plows, so that it does not become overgrown with weeds? For a good farmer works his field with daily activity and diligent care, and protects his own fields; lest a wild boar from the forest devastate them, and a cunning thief snatch away the ripe fruits. …

Commentaries on the Twelve Davidic Psalms ↗

Thomas Aquinas

"Hope in the Lord." And because temporal prosperity consists in three things -- namely, in riches, pleasures, and honors (1 Jn. 2: "All that is in the world," etc.) -- therefore, inasmuch as spiritual prosperity also consists in three things, he does three things. First, riches are set forth; second, pleasures, at "Delight"; third, glory, at "He will bring forth," which God promises to those who hope in him. Regarding the first, he does three things. …

Exposition on the Psalms of David ↗