23 The Hebrew word refers to an expanse of air pressure between the surface of the sea and the clouds, separating water below from water above. In v. 8 it is called “sky.” An expanse. In the poetic texts the writers envision, among other things, something rather strong and shiny, no doubt influencing the traditional translation “firmament” (cf. “dome”). Job 37:18 refers to the skies poured out like a molten mirror. Dan 12:3 and Ezek 1:22 portray it as shiny. The sky or atmosphere may have seemed like a glass dome. For a detailed study of the Hebrew conception of the heavens and sky, see L. I. J. Stadelmann, The Hebrew Conception of the World (), 37–60.
24 Heb “the waters from the waters.”

In other versions

And God said, “Let there be an expanse in the midst of the waters, and let it separate the waters from the waters.”

And God said, “Let there be a vault between the waters to separate water from water.”

Then God said, “Let there be an expanse between the waters, separating water from water.”

Then God said, “Let there be a space between the waters, to separate the waters of the heavens from the waters of the earth.”

And God said, “Let there be a vaulted dome in the midst of the waters, and let it cause a separation between the waters.”

And God said, Let there be a firmament in the midst of the waters, and let it divide the waters from the waters.

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