Charles H. Spurgeon on Psalms 41:13

Amen and Amen. As the Psalms were not written by one man, so neither do they form one book. The Psalter is, in fact, a Pentateuch, and the lines of demarcation, which divide the five books one from another, are clear and distinct enough. At the end of the 41st Psalm, of the 72nd, of the 89th, and of the 106th, we meet with the solemn, Amen, single or redoubled, following on a doxology, which indicates that one book ends and that another is about to begin. A closer study of the Psalms shows that each book possesses characteristics of its own. Jehovah ("the Lord") for example, is prominent as the divine name in the first book, Elohim ("God") in the second. E. H. Plumptre, M.A., in "Biblical Studies, "1870.