The refrain of Psalm 136 is “for His steadfast love endures forever!” It is repeated 26 times and is the major theme of the Psalm. The refrain is the part that the people say, after the priest said the first part of each verse. That interaction between the priest and the people is the antiphon part of this Psalm – it’s a responsive reading. Whether the people sang it or spoke it, it is a powerful confession of God’s goodness, grace, and mercy.