To do justice to the biblical book of Psalms, we must respect the diversity represented in this collection. It contains some of the oldest literature in the Old Testament and some of its most recent, thus spanning several centuries. The psalms stem from a variety of social circles and traditions: the royal court, priests, Levites, prophets, wise sages, and the poor. And psalms reflect a variety of purposes: to praise, pray, testify, teach, crown a king, etc. - Introduction.