Have mercy opon me, O God - This is the utterance of a full heart; a heart crushed and broken by the consciousness of sin. The psalmist had been made to see his great guilt; and his first act is to cry out for mercy. There is no attempt to excuse his sin, or to apologise for it; there is no effort to vindicate his conduct; there is no complaint of the righteousness of that holy law which condemned him. It was “guilt” that was before his mind; guilt only; deep and dreadful guilt. The appeal properly expresses the state of a mind that is overwhelmed at the remembrance of crime, and that comes with earnestness to God to plead for pardon. The only hope of a sinner when crushed with the consciousness of sin is the mercy of God; and the plea for that mercy will be urged in the most earnest and impassioned language that the mind can employ. “Accordingly to thy Iovingkindness.” On the meaning of the word used here, see the notes at Psalms 36:7.
(a) The “ground” of his hope was the compassion of God:
(b) the “measure” of that hope was His boundless beneficence; or, in other words, he felt that there was need of “all” the compassion of a God.
His sin was so great, his offence was so aggravated, that he could have no hope but in a Being of infinite compassion, and he felt that the need of mercy in his case could be measured and covered “only” by that infinite compassion.
According unto the multitude of thy tender mercies - The same idea occurs here also. The psalmist fixed his eye on the “vastness” of the divine mercy; on the numberless “acts” of that mercy toward the guilty; here he found his hope, and here alone. Every instance of extraordinary mercy which had occurred in the world furnished him now with an argument in his appeal to God; was an encouragement to him “in” that appeal; was a ground of hope that his appeal would not be rejected. So to us: every instance in which a great sinner has been forgiven is evidence that we may be forgiven also, and is an encouragement to us to come to God for pardon. See the notes at 1 Timothy 1:16.
Blot out my transgressions - In allusion to an account that is kept, or a charge made, when such an account is wiped away, erased, or blotted out. Compare Exodus 32:32-33; see the notes at Isaiah 43:25; notes at Isaiah 44:22; notes at Colossians 2:14. Never was a more earnest appeal made by a sinner than that which is made in this verse; never was there a more sincere cry for mercy. It shows us where we should “begin” in our prayers when we are pressed down with the consciousness of sin - with a cry for “mercy,” and not an appeal to “justice;” it shows us what is to be the “ground” and the “measure” of our hope - the mere compassion of an infinitely benevolent God; it shows us the place which we must take, and the argument on which we must rely - a place among sinners, and an argument that God has been merciful to great sinners, and that therefore he may be merciful to us.