13 Blessed be Jehovah, the God of Israel, for ever and ever (111) Here the Psalmist confirms and repeats the expression of thanksgiving contained in a preceding verse. By calling God expressly the God of Israel, he testifies that he cherished in his heart a deep and thorough impression of the covenant which God had made with the Fathers; because it was the source from which his deliverance proceeded. The term amen is repeated twice, to express the greater vehemence, and that all the godly might be the more effectually stirred up to praise God.
(111) The Hebrew Psalter is divided into five books. This is the end of the first book. The second ends with the 72d psalm, the third with the 89, the fourth with the 106, and the fifth with the 150. It is worthy of remark, that each of these five books solemnly concludes with a distinct ascription of praise to God; only no distinct doxology appears at the end of the fifth book, probably because the last psalm throughout is a psalm of praise. The Jewish writers affirm that this form of benediction was added by the person who collected and distributed The Psalms into their present state. How ancient this division is, cannot now be clearly ascertained. Jerome, in his Epistle to Marcella, and Epiphanius, speak of The Psalms as having been divided by the Hebrews into five books; but when this division was made, they do not inform us. The forms of ascription of praise, added at the end of each of the five books, are in the Septuagint version, from which we may conclude that this distribution had been made before that version was executed. It was probably made by Ezra, after the return of the Jews from Babylon to their own country, and the establishment of the worship of God in the new temple; and it was perhaps made in imitation of a similar distribution of the books of Moses. In making this division of the Hebrew Psalter, regard appears to have been paid to the subject-matter of the psalms.