Charles Ellicott Commentary Genesis 1:7

"And God made the firmament, and divided the waters which were under the firmament from the waters which were above the firmament: and it was so." — Genesis 1:7 (ASV)

God made the firmament. —This wide open expanse upon the earth’s surface, supplied by the chemistry of nature—that is, of God—with that marvelous mixture of gases which form atmospheric air, was a primary necessity for human existence and activity. In each step of the narrative, humanity is always in view; and even the weight of the overlying atmosphere is indispensable for the health and comfort of the human body, and for keeping all things in their place on earth. (See Note, Genesis 1:8.) And in this secondary sense, it may still rightly be called the firmament.

The waters which were under the firmament ... the waters which were above the firmament. —While this is a popular description of what we daily see—namely, masses of running water gathered on the earth’s surface, and above a cloudland, into which the waters rise and float—it is not contrary to, but in accordance with, science. The atmosphere is the receptacle for the waters evaporated from the earth and ocean, and by means of electrical action, it keeps these aqueous particles in a state of repulsion, and forms clouds, which the winds carry within them. The laws by which rain is formed and the earth watered are so full of thoughtful contrivance and arrangement that they are constantly referred to in the Bible as the chief natural proof of God’s wisdom and goodness. (See Acts 14:17.)

Moreover, if there were not an open expanse next to the earth, it would be wrapped in a perpetual mist, unvisited by sunshine, and the result would be as described in Genesis 2:5, that humans could not exist on earth to till the ground. The use, however, of popular language and ideas is admittedly the method of Holy Scripture, and we must not force upon the writer knowledge that humanity was to gain for itself. Even if the writer supposed that the rains were poured down from an upper reservoir, it would be no more an argument against his being inspired than Saint Mark’s expression, The sun did set (Mark 1:32), disproves the inspiration of the Gospels. For the attainment of all such knowledge, God has provided another way.