Sentence:  And God said, Let there be a <WSD>firmament</WSD> in the midst of the waters, and let it divide the waters from the waters. And God made the <WSD>firmament</WSD>, and divided the waters which were under the firmament from the waters which were above the firmament: and it was so. And God called the <WSD>firmament</WSD> Heaven. 
Meaning of the word marked with <WSD> tags:  The vault of the heavens; the sky.