John Calvin Commentary Psalms 119:58

"I entreated thy favor with my whole heart: Be merciful unto me according to thy word." — Psalms 119:58 (ASV)

I have earnestly sought your face. In this verse David asserts that he still persevered in the exercise of prayer, for without prayer faith would become languid and lifeless. The manner in which he expresses himself, which in other languages might seem unpolished, expresses for the Hebrews that familiar communication to which God admits, and even invites, his servants when they come into his presence.

He summarizes the substance of his prayers, and the sum of his desires, in a single sentence: namely, that he implored the mercy of God, the sure hope of which he had formed from his word.

Let us observe, then:

1. We are aroused from our lethargy so that we may exercise our faith by prayer.
2. The principal thing for which we ought to pray is that God, out of his free grace, may be favorable to us, regard our devotion, and grant us relief. God does, indeed, aid us in a variety of ways, and our necessities also are innumerable; still, the thing we must principally and particularly request is that he will have mercy upon us, which is the source of every other blessing.
3. So that we may not present prayers that have no meaning, let us learn that God, in all his promises, is set before us as if he were our willing debtor.