Albert Barnes Commentary Psalms 136:6

"To him that spread forth the earth above the waters; For his lovingkindness [endureth] for ever:" — Psalms 136:6 (ASV)

To him that stretched out the earth above the waters - (Genesis 1:1, Genesis 1:9); see the notes at Psalms 24:2.

For his mercy ... - As an illustration of his benignity and kindness in preparing an abode for man, and for other creatures in the world. Whatever there is of life or happiness, on the continents and islands, has resulted from that act of God when he made the dry land appear.