Charles H. Spurgeon on Psalms 37:3

Trust in the Lord. Here is the second precept, and one appropriate to the occasion. Faith cures fretting. Sight is cross-eyed, and views things only as they seem, hence her envy: faith has clearer optics to behold things as they really are, hence her peace. And do good. True faith is actively obedient. Doing good is a fine remedy for fretting. There is a joy in holy activity which drives away the rust of discontent. So shalt thou dwell in the land. In "the land" which floweth with milk and honey; the Canaan of the covenant. Thou shalt not wander in the wilderness of murmuring, but abide in the promised land of content and rest. "We which have believed do enter into rest." Very much of our outward depends upon the inward: where there is heaven in the heart there will be heaven in the house. And verily thou shalt be fed, or shepherded. To integrity and faith necessaries are guaranteed. The good shepherd will exercise his pastoral care over all believers. In truth they shall be fed, and fed on truth. The promise of God shall be their perpetual banquet; they shall neither lack in spirituals nor in temporals. Some read this as an exhortation, "Feed on truth; " certainly this is good cheer, and banishes for ever the hungry heart burnings of envy.