Charles Spurgeon Commentary Genesis 1:6-8

"And God said, Let there be a firmament in the midst of the waters, and let it divide the waters from the waters. 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. And God called the firmament Heaven. And there was evening and there was morning, a second day." — Genesis 1:6-8 (ASV)

"The firmament"—an expanse of air in which floated the waters which afterwards condensed, and fell upon the earth in refreshing showers. These waters above were divided from the waters below. Perhaps they were all one steamy conglomeration before, but now they are separated. Note those four words, and it was so. Whatever God ordains always comes. You will find that it is true of all his promises that, whatever he has said, shall be fulfilled to you, and you shall one day say of it all, and it was so.

It is equally certain concerning all his threats that what he has spoken shall certainly be fulfilled, and the ungodly will have to say and it was so. These words are often repeated in this chapter.

They convey to us the great lesson that the word of God is sure to be followed by the deed of God. He speaks, and it is done.