Save me, O God, by your name; vindicate me by your might. By appealing to God as his judge, David asserts his uprightness. And it must strike us all, that in asking the divine protection it is indispensably prerequisite we should be convinced of the goodness of our cause, as it would argue the greatest profanity in any to expect that God should patronise iniquity. David was encouraged to pray for deliverance by the goodness of his cause and his consciousness of integrity; nor did he entertain a single doubt, that on representing this to God he would act the part of his defender, and punish the cruelty and treachery of his enemies.
Surely God is my help. Such language as this may show us that David did not direct his prayers at random into the air, but offered them in the exercise of a lively faith. He points, as it were, with the finger to that God who stood at his side to defend him; and was not this an amazing illustration of the power with which faith can surmount all obstacles, and glance, in a moment, from the depths of despair to the very throne of God?
I will freely sacrifice unto you: I will praise your name, O God! for it is good.* According to his usual custom, David engages, provided deliverance should be granted, to feel a grateful sense of it; and there can be no doubt that he here promises also to return thanks to God, in a formal manner, when he should enjoy an opportunity of doing so. Though God principally looks to the inward sentiment of the heart, that would not excuse the neglect of such rites as the Law had prescribed. He would testify his sense of the favour which he received, in the manner common to all the people of God, by sacrifices, and be thus the means of exciting others to their duty by his example. And he would sacrifice freely: by which he does not allude to the circumstance, that sacrifices of thanksgiving were at the option of worshippers, but to the alacrity and cheerfulness with which he would pay his vow when he had escaped his present dangers.
We are taught by the passage that, in coming into the presence of God, we cannot look for acceptance unless we bring to his service a willing mind.
Heart Aflame: Daily Readings from Calvin on the Psalms by John Calvin