On Worship Anew a few weeks ago, the Psalm reading was a section of Psalm 136. This reminded me of something I'd realized before but hadn't thought to write about.
Every other line of the Psalm is "for his steadfast love endures forever." Here are the first three verses: "1 Give thanks to the LORD, for he is good, for his steadfast love endures forever. 2 Give thanks to the God of gods, for his steadfast love endures forever. 3 Give thanks to the Lord of lords, for his steadfast love endures forever." This refrain even punctuates the accounts of Creation and the Exodus: "6 to him who spread out the earth above the waters, for his steadfast love endures forever; 7 to him who made the great lights, for his steadfast love endures forever; 8 the sun to rule over the day, for his steadfast love endures forever; 9 the moon and stars to rule over the night, for his steadfast love endures forever... 13 to him who divided the Red Sea in two, for his steadfast love endures forever; 14 and made Israel pass through the midst of it, for his steadfast love endures forever."
This repetition of "his steadfast love endures forever" provides a sense of the surety and constancy of that "steadfast love."