"The whole divine Scripture is the teacher of virtue and true faith, but the Psalter gives a picture of the spiritual life. And, just as one who draws near to an earthly king observes the formalities in regard to dress and bearing and the correct forms of words lest, transgressing in these matters, he be deemed a boor, so he who seeks to live the good life and learn about the Saviour’s conduct in the body is by the reading of this holy book first put in mind of his own soul’s condition and then supplied with fit words for a suppliant’s use....
 
"It is possible for us, therefore, to find in the Psalter not only the reflection of our own soul’s state, together with precept and example for all possible conditions, but also a fit form of words wherewith to please the Lord on each of life’s occasions, words both of repentance and of thankfulness, so that we fall not into sin; for it is not for our actions only that we must give account before the judge, but also for our every idle word."
 
--St Athanasius the Great, Letter to Marcellinus