(abbreviated)
All Scripture, both the Old Testament and the New Testament, is inspired by God and useful for teaching (2 Tim. 3:16); The book of Psalms, for those who are attentive, contains something worthy of special note. She, like a garden, contains the plantings of all other books and with sweet singing conveys what is stated in them, but, singing about it, she also reveals her own characteristics.
In every book of Scripture the same thing is foretold about the Savior that is in all the Scriptures. This is a common subject, one and the same agreement of the Spirit. In every book of Scripture one can see prophecies, laws, narratives, and hymns. But whoever picks up the book of Psalms, reading the prophecies about the Savior with the same surprise and reverence as in other Scriptures, reads the other psalms as his own words. In the psalms (an amazing thing!) whoever reads everything else, except for the prophecies about the Savior and about the pagans, seems to be pronouncing his own sayings. What is said in the psalms, the reader lifts them up to God on his own behalf, as if speaking about what he himself has done.
For the one who sings them, the psalms serve as a kind of mirror: in them he recognizes the movements of his soul and pronounces them with this thought. Each psalm is so complex and spoken by the Spirit that in the psalms we recognize the movements of our soul. For what the psalmists spoke can serve as a model and a mark for us.
And this is also the grace of the Savior. For He, having become man for our sake, brought His own Body to death for us, in order to deliver us all from death - so, wanting to show us a heavenly life pleasing to Him, He depicted it in Himself. For this reason, He not only taught, but He Himself did what He taught. Now everyone hears what the Savior is saying, and, as if looking at a picture, borrows from Him an example for their activities, when the Lord says: Learn from Me, for I am meek and lowly in heart (Matthew 11:29). And it is impossible to find a teaching about virtue more perfect than that which the Lord depicted in Himself. And patience, and love for mankind, and kindness, and courage, and mercy, and truth - you will find everything in the Lord, so that whoever observes the human life of the Lord will not lack anything for virtue. The Lord, as truly the Lord of all, who cares for those created by Him, not only lays down the law, but also gives Himself as a model, so that those who wish may know the power to carry it out in practice.
That is why, even before His coming to us, He inspired the psalmists, so that, just as He showed in Himself the earthly and heavenly man, so those who wish could study the spiritual movements and dispositions in the psalms, finding in them both healing and correction of every movement.
It is undeniable that all Holy Scripture teaches virtue and true faith; the book of Psalms, as it were, represents in a picture how the soul should behave. Just as a person who must appear before the king tries to find out in advance how he should behave and what to say, so that, having accidentally said the wrong thing, he will not fall under condemnation, so he who strives for virtue and wants to know the life of the Savior in the flesh first, by reading this book, renews in his memory the events of Sacred History, brings the soul into the proper disposition, and thus learns, guided by it. Anyone who reads the psalms will find in them examples of those words with which one can please the Lord, correct oneself and offer thanksgiving praise to the Lord. Anyone who turns to God in words other than those given in the psalms runs the risk of falling into wickedness: after all, it is said that not only for deeds, but also for every idle word that people speak, they will give an answer on the day of judgment (Matthew 12:36).
For this purpose, some of the psalms are presented in the form of a narrative, others - exhortations, others - in the form of a prophecy, others - in the form of a prayer, and others - in the form of a confession.
Let us not remain silent about why the words of the psalms are chanted. Many ordinary people think that chanting psalmody was introduced to delight the ears. But this is not true: Scripture does not care about pleasantness and sweetness, but about spiritual benefit, and for this purpose singing was established.
There are various movements in the soul; there is in it a thinking, lustful and irritable force; these forces activate the bodily members. Reason demands that a person should not be in discord and discord with himself and that the soul, according to the word of the Apostle, having the mind of Christ (1 Cor. 2:16), should be guided by this leader and restrain its passions by him, dominate over the bodily members, bringing them into obedience to reason, and that, like a tuned instrument in the hands of a musician, the person himself, listening to the spirit, would be entirely obedient to God’s will in all members and movements and serve to her. And the image and likeness of such a harmonious and calm state of thoughts is the harmonious pronunciation of the psalms. We express our spiritual thoughts through the words we speak; and the Lord, wanting the sweet sound of words to serve as a symbol of spiritual harmony in the soul, established to sing decorously and recite psalms. This is the need of a soul that is in a good disposition, according to the word of Scripture: If anyone in you rejoices, let him sing (James 5:13).
Therefore, those who read divine songs in a different way sing psalms unreasonably: they only delight themselves and thereby bring upon themselves censure: Praise is unpleasant in the mouth of a sinner, for it was not sent from the Lord (Sir. 15:9). And those who sing in the above-mentioned way - so that the euphony of their words stems from the good mood of the soul and from its agreement with the spirit - sing not only with their lips, but also with their minds and bring great benefit not only to themselves, but also to those who want to listen to them.
So, the recitation of psalms does not come from an external desire for euphony, but serves as a sign of harmony of thoughts in the soul. Reading brought to a harmonious measure is a symbol of a well-disposed and non-stormy state of mind. And the ancient custom of praising God with good cymbals, with psalms and harps (Ps. 150:3-5) was also a symbol that the bodily members were brought into the correct combination, like strings, and the thoughts of the soul became like cymbals, and all this was set in motion and animated by the voice and spirit of the mouth, so that man, according to the word of Scripture, lives and mortifies by the spirit works of the flesh (Rom. 8:13). Thus, whoever sings psalms correctly brings his soul into harmony and, as it were, makes it smooth from an uneven one - and the soul, having come to a state in accordance with its nature, fears nothing, but becomes more capable of vivid ideas, acquires a greater desire for future benefits and, tuned by the euphony of the sayings, forgets passions and, thinking better, is blissfully united with the mind that abides in Christ.
Therefore, child, everyone who reads this book should read everything in it with sincere disposition, because everything in it is inspired by God; and moreover, to extract from it, as from a garden, for his own benefit, exactly what he sees as a need for himself. Whether repentance or confession is needed, whether sorrow or temptation has befallen someone, whether someone is persecuted or has gotten rid of evil intentions, whether someone is sad or confused or sees himself prospering and the enemy defeated, or whether he intends to praise, give thanks and bless the Lord - for all this he will find instruction in the divine psalms.
Let no one try to alter or even change the expressions of the psalms, seeking external eloquence - but let him simply read and sing what is written as it is written, so that the saints who served us in this, recognizing their words, pray with us - it is better to say that the Spirit himself, who spoke in the saints, hearing the very words that He inspired to the saints, becomes our helper. For to the extent that the life of the saints is better than the life of others, to the same extent the sayings they used are better and stronger than those composed by us. For by this they pleased God and, by saying all this, as the apostle said, they conquered kingdoms, did righteousness, received promises, stopped the mouths of lions, quenched the power of fire, escaped the edge of the sword, were strengthened from weakness, were strong in war, drove away the armies of strangers; wives received their dead resurrected (Heb. 11:33-35).