en_tn_condensed/psa/148/004.md

Praise him, highest heaven

The phrase "highest heaven" is an idiom that refers to heaven itself. The writer speaks to heaven as if it were a person and commands it to praise Yahweh. Alternate translation: "Praise Yahweh, highest heaven, as people do" (See: rc://en/ta/man/translate/figs-personification)

you waters that are above the sky

The writer speaks to "the waters that are above the sky" as if they are people and commands them to praise Yahweh. The verbal phrase can be supplied from the previous line. Alternate translation: "praise him, you waters that are above the sky, as people do" (See: rc://en/ta/man/translate/figs-personification and rc://en/ta/man/translate/figs-ellipsis)

waters that are above the sky

The writer speaks of a place above the sky where water is stored and from which the rain comes.