Genesis 1:6-8

And God said, “Let there be an expanse [of the sky] in the midst of the waters, and let it separate the waters [below the expanse] from the waters [above the expanse].” And God made the expanse [of sky] and separated the waters which were under the expanse from the waters which were above the expanse; and it was so [just as He commanded]. God called the expanse [of sky] heaven. And there was evening and there was morning, a second day.