For most of the Reformers, as with much of the preceding exegetical tradition, the Psalms played an oversized role in the lives of individual believers and the collective church. They were central to devotion and worship, and they were understood as a précis of the entire Scripture, encapsulating the whole story of God and his people, as well as a window into the human soul, as the covenant is worked out through a range of events and emotions. Martin Luther’s (1483-1546) adherence to this tradition is made clear in his preface to the Psalms, where he gives a powerful and poetic introduction to the book and its significance to the Christian life.
Commentary on Psalms
The Psalter ought to be a precious and beloved book because it promises Christ’s death and resurrection so clearly—and depicts his kingdom and the condition and nature of all Christendom—that it might well be called a little Bible. Most beautifully and briefly it contains everything that is in the entire Bible; it is made into a fine enchiridion or handbook. It seems to me that the Holy Spirit himself wanted to take the trouble to compile a short Bible and example-book of all Christendom or all the saints, so that anyone who could not read the whole Bible would have here almost an entire summary of it, comprised in one dear little book. . . .
In sum, do you want to see the holy Christian church painted in living color and form, comprised in one little picture? Then pick up the Psalter! There you have a fine, bright, pure mirror that will show you what Christendom is. Yes, you will even find yourself in it and the true gnōthi seauton (“know yourself ”), as well as God himself and all creatures.
Psalms 1-72, ed. Herman J. Selderhuis, Reformation Commentary on Scripture OT vol. 7, 2.