Genesis 1:6-8

6 And Elohim said, “Let an expanse come to be in the midst of the waters, and let it separate the waters from the waters.”

7 And Elohim made the expanse, and separated the waters which were under the expanse from the waters which were above the expanse. And it came to be so.

8 And Elohim called the expanse ‘heavens.’ And there came to be evening and there came to be morning, the second day.