1 This Psalm is the first of those to which is prefixed the word Allelujah; the meaning of which word, or rather two words, is, Praise the Lord. For this reason he begins with praises: “O confess unto the Lord, and call upon His Name”; for this confession is to be understood as praise, just as these words of our Lord, “I confess to You, O Father, Lord of heaven and earth.” For after commencing with praise, calling upon God is wont to follow, whereunto he that prays does next add his longings: whence the Lord's Prayer itself has at the commencement a very brief praise, in these words, “Our Father which art in Heaven.” The things prayed for, then follow....This also follows, “Tell the people what things He has done;” or rather, to translate literally from the Greek, as other Latin copies too have it, “Preach the Gospel of His works among the Gentiles.” Unto whom is this addressed, save unto the Evangelists in prophecy?
2. “O sing unto Him, and play on instruments unto Him”. Praise Him both by word and deed; for we sing with the voice, while we play with an instrument, that is, with our hands. “Let your talking be of all His wondrous works. Be praise in His holy Name”. These two verses may without any absurdity seem paraphrases of the two words above; so that, “Let your talking be of all His wondrous works,” may express the words, “O sing unto Him;” and what follows, “be ye praised in His holy Name,” may be referred to the words, “and play on instruments unto Him;” the former relating to the “good word” wherewith we sing unto Him, in which His wondrous works are told; the latter to the good work, in which sweet music is played unto Him, so that no man may wish to be praised for a good work on the score of his own power to do it. For this reason, after saying, “be ye praised,” which assuredly they who work well deservedly may, he added, “in His holy Name,” since “he that glories, let him glory in the Lord.”...This is to be praised in His holy Name. Whence we read also in another Psalm: “My soul shall be praised in the Lord: let the meek hear thereof, and be glad;” which here in a sense follows, “Let the heart of them rejoice that seek the Lord:” for thus the meek are glad, who do not rival with a bitter jealousy those whom they imitate as already workers of good.
3. “Seek the Lord, and be strengthened”. This is very literally construed from the Greek, though it may seem not a Latin word: whence other copies have, “be ye confirmed;” others, “be ye corroborated.”...While these words, then, “Come unto Him, and be enlightened,” apply to seeing; those in the text relate to doing: “Seek the Lord, and be strengthened.”...But what means, “Seek His face evermore”? I know indeed that to cling unto God is good for me; but if He is always being sought, when is He found? Did he mean by “evermore,” the whole of the life we live here, whence we become conscious that we ought thus to seek, since even when found He is still to be sought? To wit, faith has already found Him, but hope still seeks Him. But love has both found Him through faith, and seeks to have Him by sight, where He will then be found so as to satisfy us, and no longer to need our search. For unless faith discovered Him in this life, it would not be said, “Seek the Lord.” Also, if when discovered by faith, He were not still to be diligently sought, it would not be said, “For if we hope for that we see not, then do we with patience wait for it.”...And truly this is the sense of the words, “Seek His face evermore;” meaning that discovery should not terminate that seeking, by which love is testified, but with the increase of love the seeking of the discovered One should increase.
4. “Remember,” he says, “His marvellous works that He has done, His wonders, and the judgments of His mouth”. This passage seems like that, “You shall say unto the children of Israel, I Am has sent me unto you:” an expression which, in ever so small part, scarce a mind takes in. Then mentioning His own Name, He mercifully mingled in His grace towards men, saying, “I am the God of Abraham, the God of Isaac, and the God of Jacob; this is My Name for ever.” By which He would have it to be understood, that they whose God He declared Himself lived with Him for ever, and He said this, which might be understood even by children, that they who by the great powers of love knew how to seek His face for evermore, might according to their capacity comprehend, I Am that I Am.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)