John Calvin Commentary Psalms 109:21

"But deal thou with me, O Jehovah the Lord, for thy name`s sake: Because thy lovingkindness is good, deliver thou me;" — Psalms 109:21 (ASV)

And thou, O Jehovah my Lord! From pouring out complaints and imprecations against his enemies, the Psalmist transitions to prayers. Or rather, after having turned to God as his guardian and deliverer, he appears to use this circumstance to encourage himself in prayer, just as all the pious reflections by which the faithful exercise and strengthen their faith stimulate them to call upon the name of God.

At the same time, he does not pride himself on any service he has done for God, as if deserving His help, nor does he rely on his own worthiness. Instead, he places all his confidence in the free grace and mercy of God. The integrity of which he was conscious, he set against his enemies to make their iniquity more manifest. However, he does not seek any reward from God, because he adopts the nobler principle of owing everything to God’s voluntary choice, on which he also acknowledges his safety depends.

If it were lawful for anyone to boast of his virtues and merits, certainly David was not the one least entitled to do so; and moreover, he was the representative of Christ and of the whole Church. Thus, it follows that all our prayers will vanish into smoke unless they are grounded on the mercy of God.

The case of Christ was indeed a unique one, since it was by His own righteousness that He appeased His Father's wrath towards us. However, as His human nature was entirely dependent on the good pleasure of God, so, by His own example, it was His will to direct us to the same source.

What can we do, since even the most upright among us is compelled to acknowledge that he is chargeable with much sin—surely we can never make God our debtor? Therefore, it follows that God, because of the kindness of His nature, takes us under His protection; and that, because of the goodness of His mercy, He desires that His grace may shine forth in us.

In coming to God, we must always remember that we must possess the testimony of a good conscience and must beware of harboring the thought that we have any inherent righteousness that would make God our debtor, or that we deserve any reward from Him. For if, in the preservation of this short and frail life, God manifests the glory of His name and His goodness, how much more ought all confidence in good works to be laid aside when the subject concerns heavenly and eternal life?

If, in prolonging my life for a short time on earth, His name is thereby glorified by manifesting His kindness and generosity towards me of His own accord; and when, therefore, having delivered me from the tyranny of Satan, He adopts me into His family, washes away my impurity in the blood of Christ, regenerates me by His Holy Spirit, unites me to His Son, and leads me to the life of heaven—then, assuredly, the more bountifully He treats me, the less should I be disposed to arrogate to myself any portion of the praise.

How differently David acts, who, to procure favor for himself, makes known his own poverty and misery?

And since outward affliction is of no avail unless a man is humbled at the same time, and his proud and rebellious spirit is subdued, the Psalmist here repeats that his heart was wounded within him. From this we may learn that God will be a physician to no one except to those who, in a spirit of genuine humility, send up their sighs and groans to Him and do not become hardened by their afflictions.