6 “O Lord, the very Heavens shall praise Your wondrous works”. The Heavens will not praise their own merits, but Your wondrous works, O Lord. For in every act of mercy on the lost, of justification of the unrighteous, what do we praise but the wondrous works of God? Thou praisest Him, because the dead have risen: praise Him yet more, because the lost are redeemed. What grace, what mercy of God! You see a man yesterday a whirlpool of drunkenness, today an ornament of sobriety: a man yesterday the sink of luxury, today the beauty of temperance: yesterday a blasphemer of God, today His praiser: yesterday the slave of the creature, today the worshipper of the Creator. From all these desperate states men are thus converted: let them not look at their own merits: let them become Heavens, and praise the wondrous works of Him by whom they were made Heavens....
Source: The Enarrations, or Expositions, on the Psalms (New Advent)