Kommentar zu Bereschit 1:6

יהי רקיע BE THERE AN EXPANSE — Let the expansion become fixed; for although the heavens were created on the first day, they were still in a fluid form, and they became solidified only on the second day at the dread command (literally, rebuke) of the Holy One, blessed be He, when he said “Let the firmament be stable” (Genesis Rabbah 4:2). It is to this that allusion is made in what is written in (Job 26:11): “The pillars of heaven were trembling” (i. e. they were unstable) — this was during the whole of the first day — and on the second (Job 26:11): “they were astonished at His rebuke”, like a man who stands immovable, amazed at the rebuke of one who terrifies him.

ויאמר אלוקים יהי רקיע, after the first day had been concluded with its morning, G’d issued a new directive.

יהי רקיע בתוך המים, let there be טבע, i.e. guidelines, rules governing the function of what is below and what is above the primordial waters. Just as there are such parameters surrounding our world, i.e. the globe we call “earth,” so there should be similar guidelines governing what is below the atmosphere and earth itself. The region in which air exists should become clearly defined. [the gaseous nature of air should not be allowed to escape into all directions of the universe beyond our globe so that creatures on earth would die from the lack of air. In other words, the atmosphere should be “enclosed” whether by gravitational or other forces is immaterial. Ed.] At the same time, air should be given enough space within which “to breathe,” so to speak.