Matthew Henry on Psalms 107:17-22

If we knew no sin, we should know no sickness. Sinners are fools. They hurt their bodily health by intemperance, and endanger their lives by indulging their appetites. This their way is their folly. The weakness of the body is the effect of sickness. It is by the power and mercy of God that we are recovered from sickness, and it is our duty to be thankful. All Christ's miraculous cures were emblems of his healing diseases of the soul. It is also to be applied to the spiritual cures which the Spirit of grace works. He sends his word, and heals souls; convinces, converts them, makes them holy, and all by the word. Even in common cases of recovery from sickness, God in his providence speaks, and it is done; by his word and Spirit the soul is restored to health and holiness.