6 “But I have hoped in Your mercy”. Because this very thing, that a man be not moved, and that he abide fixed in the Lord, he should not attribute to self: lest when he glories that he has not been moved, he be moved by this very pride. “My heart shall exult in Your salvation;” in Christ, in the Wisdom of God. “I will sing to the Lord who has given me good things;” spiritual good things, not belonging to man's day. “And I will chant to the name of the Lord most high”; that is, I give thanks with joy, and in most due order employ my body, which is the song of the spiritual soul. But if any distinction is to be marked here, “I will sing” with the heart, “I will chant” with my works; “to the Lord,” that which He alone sees, but “to the name of the Lord,” that which is known among men, which is serviceable not for Him, but for us.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)