John Calvin Commentary Psalms 18:1

"I love thee, O Jehovah, my strength." — Psalms 18:1 (ASV)

And he said, etc. I will not stop to examine too minutely the syllables, or the few words, in which this psalm differs from the song recorded in 2 Samuel 22. When, however, we encounter any important difference, we will address it in the proper place. We find one such difference in the remarkable sentence with which this psalm begins: I will love you affectionately, O Jehovah, my strength, which is omitted in the song in Samuel.

As Scripture does not use the verb רהם, racham, for to love, except in the conjugation pihel, and as it is here put in the conjugation kal, some of the Jewish expositors explain it as meaning to seek mercy; as if David had said, "Lord, since I have so often experienced you to be a merciful God, I will trust and rest in your mercies forever."

Certainly, this exposition would not be unsuitable, but I am unwilling to depart from the other, which is more generally received. It is to be observed that love to God is presented here as constituting the principal part of true godliness, for there is no better way of serving God than to love him.

No doubt, the service which we owe him is better expressed by the word reverence, so that his majesty may be prominent in our view in its infinite greatness. But as he requires nothing so expressly as to have all the affections of our heart directed towards him, there is no sacrifice he values more than when we are firmly bound to him by the chain of a free and spontaneous love. On the other hand, there is nothing in which his glory shines forth more conspicuously than in his free and sovereign goodness. Moses, therefore (Deuteronomy 10:12), when he intended to give a summary of the law, says:

“And now, Israel, what does the Lord your God require
of you but to love him?”

In saying this, David also intended to show that his thoughts and affections were not so intently fixed on God's benefits as to be ungrateful to their author—a sin that has been all too common in every age.

Even today, we see how most people casually enjoy God's gifts without paying any regard to him, or, if they think of him at all, it is only to despise him. David, to prevent himself from falling into this ingratitude, in these words makes, so to speak, a solemn vow: "Lord, as you are my strength, I will continue united and devoted to you by unfeigned love."