John Calvin Commentary Psalms 38:15

"For in thee, O Jehovah, do I hope: Thou wilt answer, O Lord my God." — Psalms 38:15 (ASV)

For on thee, O Jehovah! do I wait. David here shows the source of his patience. It consisted in this: trusting in the grace of God, he overcame all the temptations of the world. And certainly, the mind of man will never be formed to gentleness and meekness, nor will he be able to subdue his passions, until he has learned never to give up hope.

The Psalmist, at the same time, adds that he cherished his hope by constant meditation, so that he would not yield to despair. And this is the only means of our perseverance: when, on the ground of his own promises which he has given us, we appeal to him—or rather, when, by setting before our view his fidelity and his constancy in fulfilling what he has promised, we assure ourselves of his faithfulness.

Accordingly, Paul, in Romans 5:4, very properly joins patience to hope and consolation. The repetition of terms in this verse shows that this holy man was subjected to a severe and arduous conflict. Thou, he says, O Lord! my God, wilt answer me. His language implies that if God should delay to come to his help, there was reason to fear that he would faint from weariness or fall into despair, unless, setting this double defense before him, he persevered valiantly in the conflict.