From the additional notes to Charles Spurgeon's The Treasury of David, Psalm 109.
Verse 21. For thy name's sake. It does not say, For my name, that it may be vindicated from, reproach and shame: but for Thy name; as if he would say, whatever I may be, O Lord, and whatever may befall me, have respect to Thy name, have regard to it only. I am not worthy, that I should seek Thy help, but Thy name is worthy which thou mayest vindicate from contempt. We learn here with what passion for the glory of the divine name they ought to be animated, who are peculiarly consecrated to the name of God. He does not say, "Because my case is good", but because thy mercy is good. Note this also, he does not simply say, Because thou art good, or because thou art merciful; but because thy mercy is good. He had experienced a certain special goodness in the Divine mercy; i.e., such timeliness, kind readiness in all afflictions, and help for every kind of affliction prepared and provided. On this he rests hope and confidence, in this takes refuge. All those are truly happy who have had experience of this mercy, and can depend on it with firm hope and confidence.—Wolfgang Musculus.