The _fourth_ book includes Psalms 90-106. Of these seventeen psalms, only three bear titles; the ninetieth being referred to Moses, the hundred and first and hundred and third to David. This book is therefore emphatically one of anonymous psalms, which are for the most part of a very general character, being evidently arranged with reference to the service of song in the sanctuary. Throughout this book the divine name _Jehovah_ prevails; the name _Elohim_, _God_, being rarely used except in connection with a pronoun or some epithet--_my God_, _God of Jacob_, etc. The _fifth_ book contains the remaining forty-four psalms. Of these, fifteen are ascribed to David; one to Solomon (Psa. 127); and twenty-eight are anonymous. In this book also the divine name _Jehovah_ prevails almost exclusively. It is probable that these five books were arranged not simultaneously but successively, with considerable intervals between some of them. The subscription appended to the second book: "The prayers of David the son of Jesse are ended," may possibly be explained, upon this supposition. It may have been added as a subscription to the first two books, before the others were arranged for the temple service. Although the psalms belonging to the respective books are not classified upon any strict principle, yet their arrangement is not altogether fortuitous. We find psalms with the same title grouped together--eleven psalms of Asaph. (73-83); eight of the sons of Korah (42-49); eight of David (139-145 separated from his other psalms); three psalms inscribed _Al-taschith_ (57-59); the fifteen songs of degrees (120-134), etc. Also we find psalms of similar contents grouped together--Psa. 79, 80; 88, 89; 91-100; 105-107; etc. Various attempts have been made to classify the psalms according to their subjects. But their very richness and variety makes this a very difficult undertaking. They cover the whole field of religious experience for both individual believers and the church at large. Many of them--the so-called _Messianic_ psalms--are prophetic of the Saviour's offices and work. We need not wonder, therefore, that the Psalms are quoted in the New Testament oftener than any other book of the Old Testament, Isaiah not excepted. 11. Besides the names of the authors, or the occasion of their composition, many of the psalms bear other inscriptions. Of these the principal are the following: (1.) The _dedicatory title: To the chief musician_, prefixed to fifty-three psalms, signifies that the psalm is assigned to him, as the leader of the choir at the tabernacle or temple, to be used in the public worship of God. The title rendered in our version: _For the sons of Korah_, is better translated, as in the margin: _Of the sons of Korah_; that is, written by one of their number.