Moses, when he related the deeds of the patriarchs, did so in a plain and unadorned style.
But when he had miraculously led the people of Israel across the Red Sea, when he had seen King Pharaoh drowned with all his army, he transcended his own skills (just as the miracle had transcended his own powers) and he sang a triumphal song to the Lord.
Miriam the prophetess herself took up a timbrel and led the others in the refrain: Sing to the Lord: he has covered himself in glory, horse and rider he has thrown into the sea.
History instructs us, the law teaches us, prophecy foretells, correction punishes, morality persuades; but the book of psalms goes further than all these.
It is medicine for our spiritual health.
Whoever reads it will find in it a medicine to cure the wounds caused by his own particular passions.
Whoever studies it deeply will find it a kind of gymnasium open for all souls to use, where the different psalms are like different exercises set out before him.
In that gymnasium, in that stadium of virtue, he can choose the exercises that will train him best to win the victor’s crown.
If someone wants to study the deeds of our ancestors and imitate the best of them, he can find a single psalm that contains the whole of their history, a complete treasury of past memories in just one short reading.
If someone wants to study the law and find out what gives it its force (it is the bond of love, for whoever loves his neighbor has fulfilled the law) let him read in the psalms how love led one man to undergo great dangers to wipe out the shame of his entire people; and this triumph of virtue will lead him to recognise the great things that love can do.
And as for the power of prophecy – what can I say? Other prophets spoke in riddles. To the psalmist alone, it seems, God promised openly and clearly that the Lord Jesus would be born of his seed: I promise that your own son will succeed you on the throne.
Thus in the book of psalms Jesus is not only born for us: he also accepts his saving passion, he dies, he rises from the dead, he ascends into heaven, he sits at the Father’s right hand.
The Psalmist announced what no other prophet had dared to say, that which was later preached by the Lord himself in the Gospel.
Ambrose of Milan (c. 337-397): Explanations of the Psalms (Psalm 1, 4.7-8; CSEL 64, 4-7) from the Office of Readings for Friday of the 10th Week in Ordinary Time @ Crossroads Initiative.