Charles Ellicott Commentary Psalms 148:4

"Praise him, ye heavens of heavens, And ye waters that are above the heavens." — Psalms 148:4 (ASV)

Heavens of heavens. —See Psalms 68:33, and references.

Before passing downwards to the earth, the invocation pauses to combine all the heights. These heights have been previously addressed in the expression which denotes their position relative to the earth. This includes the highest heaven of all, and then the world of water which, in the Hebrew conception of the Cosmos, was supposed to be the foundation, while itself rests on the firmament or heavenly vault. (See Psalms 104:3.)