John Calvin Commentary Psalms 37:18

"Jehovah knoweth the days of the perfect; And their inheritance shall be for ever." — Psalms 37:18 (ASV)

Jehovah knows the days of the upright. It is not without good reason that David so frequently stresses this doctrine: that the righteous are blessed because God provides for their needs. We see how prone people are to distrust, and how much they are troubled by an excess of cares and anxieties from which they are unable to free themselves. On the other hand, they fall into another error by being more anxious about the future than is necessary. And yet, however active and industrious they are in forming their plans, they are often disappointed in their expectations and frequently fail altogether to succeed.

Therefore, nothing is more beneficial for us than to keep our eyes continually fixed on the providence of God, which alone can best provide for us everything we need. For this reason, David now says that God knows the days of the righteous; meaning, he is not ignorant of the dangers to which they are exposed and the help they need.

We should use this doctrine as a source of comfort in every trial that may seem to threaten us with destruction. We may be troubled in various ways and beset by many dangers that threaten us with death at any moment. But this thought should be a sufficient source of comfort for us: not only are our days numbered by God, but he also knows all the changing circumstances of our lives on earth.

Since God, then, so carefully watches over us to maintain our well-being, we should enjoy, in this our journey on earth, as much peace and satisfaction as if we were in full possession of our paternal inheritance and home. Because God cares for us, David concludes from this that our inheritance is everlasting.

Furthermore, by declaring that those who are upright are so carefully protected by God, he urges us to sincerely pursue truth and uprightness. If we desire to be kept safe under God’s protection, we should cultivate meekness and utterly reject this hellish proverb: “We must howl among wolves.”