“… for His steadfast love endures forever…” Twenty-six times in Psalm 136 this phrase ends a couplet. In Bible study, anytime God repeats Himself, it is considered a standard practice to take that as an emphasis of the point being repeated.
All that is said in this chapter emphasizes His steadfast love continues, does not end, is eternal, abiding, enduring. The chapter moves from His goodness, His God-ness, His Supremacy, into His uniqueness, His creativity, His ability to accomplish His purposes for His people, to sustain His promises and ends by acknowledging His care for those accepting His lordship.
Above all and in all, ‘Give thanks to the God of Heaven, for His steadfast Love endures forever.’
Amen. And Amen.