Moses
Genesis 1:7ESV·traditional attribution

And God made the expanse and separated the waters that were under the expanse from the waters that were above the expanse. And it was so.

Matthew Henry Presbyterian @wholebiblehenry

We have here an account of the second day's work, the creation of the firmament, in which observe, 1. The command of God concerning it: Let there be a firmament, an expansion, so the Hebrew word signifies, like a sheet spread, or a curtain drawn out.

Commenting on Genesis 1:6-8

John Gill Reformed Baptist @doctorgill

And God made the firmament,.... By a word speaking, commanding it into being, producing it out of the chaos, and spreading it in that vast space between the heaven of heavens and our earth (z), And divided the waters which were under the firmament from the waters which were above the firmament; the lower part of it, the atmosphere above, which are the clouds full...

Jamieson-Fausset-Brown Reformed @jfbcommentary

SECOND DAY. (Gen 1:6-8) firmament--an expanse--a beating out as a plate of metal: a name given to the atmosphere from its appearing to an observer to be the vault of heaven, supporting the weight of the watery clouds. By the creation of an atmosphere, the lighter parts of the waters which overspread the earth's surface were drawn up and suspended in the visible heavens, while...

Commenting on Genesis 1:6-8