Adam Clarke on Psalms 106:48

Blessed be the Lord God of Israel - Here both gratitude and confidence are expressed; gratitude for what God had already wrought, and confidence that he would finish the great work of their restoration.

From everlasting to everlasting - מן האולם ועד האולם min haolam vead haolam, "from the hidden term to the hidden term," from the beginning of time to the end of time, from eternity and on to eternity. Fra worlde and into worlde, old Psalter; which it paraphrases thus: Fra with outen beginning, &withouten endyng.

And let all the people say, Amen - Let the people join in the prayer and in the thanksgiving, that God may hear and answer. Anglo-Saxon: "And, quoth all folk, be it, be it." Hallelujah - Praise ye Jehovah! Let his name be eternally magnified! Amen.

This is the end of the fourth book of the Psalms.