Charles Ellicott Commentary Psalms 106:48

"Blessed be Jehovah, the God of Israel, From everlasting even to everlasting. And let all the people say, Amen. Praise ye Jehovah. BOOK V" — Psalms 106:48 (ASV)

Blessed ... —The doxology, which is only slightly altered from that at the end of the second book, is quoted as part of the psalm in 1 Chronicles 16:36 —an indication that by that time this book was complete, if not the whole collection.