From St. Basil the Great's homily, "A Psalm on the Lot of the Just Man"
"All Scripture is inspired by God and is useful, composed by the Spirit for this reason, namely, that we men, each and all of us, as if in a general hospital for souls, may select the remedy for his own condition. For it says, 'care will make the greatest sin to cease.' Now the prophets teach one thing, historians another, the law something else, and the form of advice found in the proverbs something different still. But, the Book of Psalms has taken over what is profitable from all. It foretells coming events; it recalls history; it frames laws for life; it suggests what must be done; and, in general, it is the common treasury of good doctrine, carefully finding what is suitable for each one. The old wounds of souls it cures completely, and to the recently wounded it brings speedy improvements; the diseased it treats and the unharmed it preserves. On the whole, it effaces, as far as is possible, the passions, which subtly exercise dominion over souls during the lifetime of man, and it does this with a certain orderly persuasion and sweetness which produces sound thoughts."