Every verse has this repeated chorus, “For His mercy endureth for ever.” Such a peculiarity is used to enforce upon our unappreciative minds, that all our benefits flow from everlasting mercy. They are covenant mercies that are sure and unceasing, and are ours because God is good. They are daily repeated to us.
We are told in the first three verses, and the last, to give thanks. The reasons being, what He is (vv. 1-3); what He is able to do (v. 4); His creative genius and power (vv. 5-9); His redemption from bondage (vv. 10-15); His providential dealings (vv. 16-22); His grace in calamity (vv. 23-24); His goodness to this world (v. 25); and that He is the God of Heaven (v. 26).
Our God is also all these to us, but only because we know His redemptive mercy through Christ Jesus.
Psalm 136 - First Version
1 Give thanks to God, for good is he: