9 “For better is Your mercy than lives.” Many are the lives of men, but one life God promises: and He gives not this to us as if for our merits but for His mercy....For what is so just a thing as that a sinner should be punished? Though a just thing it be that a sinner should be punished, it has belonged to the mercy of Him not to punish a sinner but to justify him, and of a sinner to make a just man, and of an ungodly man to make a godly man. Therefore “His mercy is better than lives.” What lives? Those which for themselves men have chosen. One has chosen for himself a life of business, another a country life, another a life of usury, another a military life; one this, another that. Divers are the lives, but “better is Your” life “than” our “lives.”...“My lips shall praise You.” My lips would not praise You, unless before me were to go Your mercy. By Your gift You I praise, through Your mercy You I praise. For I should not be able to praise God, unless He gave me to be able to praise Him.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)