Psalm 136:1 opens a unique hymn of praise, establishing the central theme of the entire psalm: giving thanks to the LORD because of his goodness and his enduring mercy (or steadfast love). This opening verse acts as a call to worship, immediately setting a tone of joyous gratitude and defining the two primary reasons for all subsequent praise—God's inherently good nature and his covenant love which lasts forever. It introduces the responsorial structure of the psalm, where this phrase of God's eternal mercy will be repeated twenty-six times, hammering home the powerful, unwavering truth that the foundation of all God's actions throughout history is his ceaseless, faithful compassion.