Charles H. Spurgeon on Psalms 109:21

Unto a truly broken, humbled sinner, the mercies that are in God, out of which he pardons, should have infinitely more of goodness and sweetness in them than the pardon itself, or all things else that are in the promises. This a soul that hath tasted how good the Lord is will instantly acknowledge. A promise of life to a condemned man is sweet, for life is sweet, as we say; but "thy lovingkindness", said David, who had tasted how good the Lord is, "is better than life", and infinitely sweeter, Ps 63:3. And again says David, Because thy mercy is good, deliver thou me. Deliverance was good; yea, but the mercy of God apprehended therewith was infinitely more good to him, which was the greatest inducement to him to seek deliverance. And indeed God's mercy doth eminently bear the style of goodness. —Thomas Goodwin.

Verse 21-25. The thunder and lightning are now as it were followed by a shower of tears of deep sorrowful complaint. —Franz Delitzsch.