John Calvin Commentary Psalms 18:28

"For thou wilt light my lamp: Jehovah my God will lighten my darkness." — Psalms 18:28 (ASV)

For you will light my lamp. In the song in Samuel, the form of the expression is somewhat more precise, for there it is said not that God lights our lamp, but that he himself is our lamp. The meaning, however, comes to the same thing, namely, that it was by the grace of God that David, who had been plunged in darkness, returned to the light.

David does not simply give thanks to God for having lit up a lamp before him, but also for having converted his darkness into light. He, therefore, acknowledges that he had been reduced to such extremity of distress, that he was like a man whose condition was forlorn and hopeless; for he compares the confused and perplexed state of his affairs to darkness.

This, indeed, by the transference of material things to spiritual things, may be applied to the spiritual illumination of the understanding; but, at the same time, we must attend to the subject David treats, so that we do not depart from the true and proper meaning. Now, as he acknowledges that he had been restored to prosperity by the favor of God, which was to him, as it were, a life-giving light, let us, after his example, regard it as certain that we will never have the comfort of seeing our adversities brought to an end unless God disperses the darkness that envelops us and restores to us the light of joy.

Let it not, however, be distressing to us to walk through darkness, provided God is pleased to serve as a lamp for us. In the following verse, David ascribes his victories to God, declaring that, under his guidance, he had broken through the wedges or phalanxes of his enemies and had taken their fortified cities by storm.

Thus we see that, although he was a valiant warrior and skilled in arms, he arrogates nothing to himself. Regarding the tenses of the verbs, let us clarify for our readers once for all that in this psalm David uses the past and future tenses interchangeably. This is not only because he includes different histories, but also because he presents to himself the things he speaks of as if they were still taking place before his eyes, and, at the same time, describes a continued course of the grace of God toward him.