3 Whichever then of these is understood, this book, in its parts of fifty Psalms each, gives an answer important and very worthy of consideration. For it seems to me not without significance, that the fiftieth is of penitence, the hundredth of mercy and judgment, the hundred and fiftieth of the praise of God in His saints. For thus do we advance to an everlasting life of happiness, first by condemning our own sins, then by living aright, that, having condemned our ill life, and lived a good life, we may attain to everlasting life. Our predestination is not wrought in ourselves, but in secret with Him, in His foreknowledge. But we are called by the preaching of repentance. We are justified in the calling of mercy and fear of judgment. He fears not judgment, who has previously attained salvation. Being called, we renounce the devil by repentance, that we may not continue under his yoke: being justified, we are healed by mercy, that we may not fear judgment: being glorified, we pass into everlasting life, where we praise God without end....The verse wherewith this Psalm concludes is the voice of life everlasting.
4. “Praise the Lord in His saints,” that is, in those whom He has glorified: “praise Him in the firmament of His power”. “Praise Him in His deeds of strength;” or, as others have explained it, “in His deeds of power: praise Him according to the multitude of His greatness”. All these His saints are; as the Apostle says, “But we may be the righteousness of God in Him.” If then they be the righteousness of God, which He has wrought in them, why are they not also the strength of Christ which He has wrought in them, that they should rise again from the dead? For in Christ's resurrection, “strength” is especially set forth to us, for in His Passion was weakness, as the Apostle says. And well does it say, “the firmament of His power.” For it is the “firmament of His power” that He “dies no more, death has no more dominion over Him.” Why should not they also be called “the works of” God's “strength,” which He has done in them: yea rather, they themselves are the works of His strength; just as it is said, “We are the righteousness of God in Him.” For what more powerful than that He should reign for ever, with all His enemies put under His feet? Why should not they also be “the multitude of His greatness”? Not that whereby He is great, but whereby He has made them great, many as they are, that is, thousands of thousands. Just as righteousness too is understood in two ways, that whereby He is righteous, and that which He works in us, so as to make us His righteousness. These same saints are signified by all the musical instruments in succession, to praise God in. For what the Psalmist began with, saying, “Praise the Lord in His saints,” that he carries out, signifying in various ways these same saints of His.
5. “Praise Him in the sound of the trumpet”: on account of the surpassing clearness of note of their praise. “Praise Him in the psaltery and harp.” The psaltery praises God from things above, the harp praises God from things below; I mean, from things in heaven, and things in earth, as He who made heaven and earth. We have already in another Psalm, explained that the psaltery has that board, whereon the series of strings rests that it may give a better sound, above, whereas the harp has it below. “Praise Him in the timbrel and choir”. The “timbrel” praises God when the flesh is now changed, so that there is in it no weakness of earthly corruption. For the timbrel is made of leather dried and strengthened. The “choir” praises God when society made peaceful praises Him. “Praise Him on the strings and organ.” Both psaltery and harp, which have been mentioned above, have strings. But “organ” is a general name for all instruments of music, although usage has now obtained that those are specially called organ which are inflated with bellows: but I do not think that this kind is meant here. For since organ is a Greek word, applied generally, as I have said, to all musical instruments, this instrument, to which bellows are applied, is called by the Greeks by another name: but it being called organ is rather a Latin and conversational usage. When then he says, “on the strings and organ,” he seems to me to have intended to signify some instrument which has strings. For it is not psalteries and harps only that have strings: but, because in the psaltery, and harp, on account of the sound from things below and things above, somewhat has been found which can be understood after this distinction, he has suggested to us to seek some other meaning in the strings themselves: for they too are flesh, but flesh now set free from corruption. And to those, it may be, he added the organ, to signify that they sound not each separately, but sound together in most harmonious diversity, just as they are arranged in a musical instrument. For even then the saints of God will have their differences, accordant, not discordant, that is, agreeing, not disagreeing, just as sweetest harmony arises from sounds differing indeed, but not opposed to one another.
6. “Praise Him on the well-sounding cymbals, praise Him on cymbals of jubilation”. Cymbals touch one another in order to sound, and therefore are by some compared to our lips. But I think it better to understand that God is in a manner praised on the cymbal, when each is honoured by his neighbour, not by himself, and then honouring one another, they give praise to God. But lest any should understand such cymbals as sound without life, therefore I think he added, “on cymbals of jubilation.” For “jubilation” that is, unspeakable praise, proceeds not, save from life. Nor do I think that I should pass over what musicians say, that there are three kinds of sounds, by voice, by breath, by striking: by voice, uttered by throat and windpipe, when man sings without any instrument; by breath, as by pipe, or anything of that sort: by striking, as by harp, or anything of that kind. None then of these kinds is omitted here: for there is voice in the choir, breath in the trumpet, striking in the harp, representing mind, spirit, body, but by similitudes, not in the proper sense of the words. When then he proposed, “Praise God in His saints,” to whom said he this, save to themselves? And in whom are they to praise God, save in themselves? For you, says he, are “His saints;” you are “His strength,” but that which He wrought in you; you are “His mighty works, and the multitude of His greatness,” which He has wrought and set forth in you. You are “trumpet, psaltery, harp, timbrel, choir, strings, and organ, cymbals of jubilation sounding well,” because sounding in harmony. All these are you: let nought that is vile, nought that is transitory, nought that is ludicrous, be here thought of. And since to savour of the flesh is death, “let every spirit praise the Lord”.
Which he was wont to use after his Sermons and Lectures.
Turn we to the Lord God, the Father Almighty, and with pure hearts offer to Him, so far as our meanness can, great and true thanks, with all our hearts praying His exceeding kindness, that of His good pleasure He would deign to hear our prayers, that by His Power He would drive out the enemy from our deeds and thoughts, that He would increase our faith, guide our understandings, give us spiritual thoughts, and lead us to His bliss, through Jesus Christ His Son our Lord, who lives and reigns with Him, in the Unity of the Holy Spirit, one God, for ever and ever. Amen.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)