To say that the book of Psalms is divided into five books would be an elusive description. The Book of Psalms is the longest book in the Bible, with 150 individual psalms. It is also one of the most diverse, since the psalms deal with such subjects as God and His creation, war, worship, wisdom, sin, evil, judgment, justice, and the coming of the Messiah.
David is listed as the author in 73 accounts, his personality and identity are displayed in many of these psalms. David wrote many of the individual psalms, but he is not the author of the entire collection. Two of the psalms (72) and (127) are attributed to Solomon, David's son and successor. Psalm 90 is a prayer assigned to Moses. Another group of 12 psalms (50) and (73—83) is ascribed to the family of Asaph. The sons of Korah wrote 11 psalms (42, 44-49, 84-85,87-88). Psalm 88 is attributed to Heman, while (89) is assigned to Ethan the Ezrahite. With the exception of Solomon and Moses, all these additional authors were priests or Levites who were responsible for providing music for sanctuary worship during David's reign. Fifty of the psalms designate no specific person as author.
A careful examination of the authorship question, as well as the subject matter covered by the psalms themselves, reveals that they span a period of many centuries. The oldest psalm in the collection is the prayer of Moses (90), a reflection on the frailty of man as compared to the eternity of God. The earliest psalm is (137), a song of lament, written during the days when the Hebrews were being held captive by the Babylonians, from about 586 to 538 B.C.
The 150 individual psalms were written by many different people across a period of a thousand years in Israel's history. They were compiled and put together in their present form by an unknown editor shortly after the captivity ended in 537 B.C.
The Book of Psalms is a collection of prayers, poems, and hymns that focus the worshiper's thoughts on God in praise and adoration. Parts of this book were used as a hymnal in the worship services of ancient Israel. The musical heritage of the psalms is demonstrated by its title. It comes from a Greek word which means "a song sung to the accompaniment of a musical instrument."
God’s provision of a Savior for His people is a recurring theme in the Psalms. Prophetic pictures of the Messiah are seen in numerous psalms. Psalm 2:1-12 portrays the Messiah’s triumph and kingdom. Psalm 16:8-11 foreshadows His death and resurrection. Psalm 22shows the Christ on the cross and presents detailed prophecies of the crucifixion, all of which were fulfilled perfectly. The glories of the Messiah and His bride are depicted in Psalm 45:6-7, while Psalms 72:6-17, 89:3-37, 110:1-7and 132:12-18 present the glory and universality of Christ reign.
One of the results of being filled with the Spirit or the word of Christ is singing. The psalms are the “songbook” of the early church that reflected the new truth in Christ.