John Calvin Commentary Genesis 7:11

"In the six hundredth year of Noah`s life, in the second month, on the seventeenth day of the month, on the same day were all the fountains of the great deep broken up, and the windows of heaven were opened." — Genesis 7:11 (ASV)

The same day were all the fountains of the great deep broken up. Moses recalls the period of the first creation to our memory; for the earth was originally covered with water, and by the singular kindness of God, the waters were made to recede, so that some space would be left clear for living creatures.

And this, philosophers are compelled to acknowledge: that it is contrary to the course of nature for the waters to subside so that some portion of the earth might rise above them. And Scripture records this among the miracles of God: that He restrains the force of the sea, as with barriers, lest it should overwhelm that part of the earth which is granted to humankind for a habitation.

Moses also says, in the first chapter, that some waters were suspended above in the heavens; and David, in like manner, declares that they are held enclosed as in a bottle. Lastly, God raised for humankind a theater in the habitable region of the earth and, by His secret power, caused the subterranean waters not to break forth to overwhelm us, and the celestial waters not to conspire with them for that purpose.

Now, however, Moses states that when God resolved to destroy the earth by a deluge, those barriers were torn up. And here we must consider the wonderful counsel of God; for He might have deposited, in certain channels or veins of the earth, as much water as would have sufficed for all the purposes of human life. But He has deliberately placed us between two graves, lest, in fancied security, we should despise that kindness on which our life depends.

For the element of water, which philosophers deem one of the principles of life, threatens us with death from above and from beneath, unless it is restrained by the hand of God. In saying that the fountains were broken up and the cataracts opened, Moses' language is metaphorical. It means that neither did the waters flow in their accustomed manner, nor did the rain distill from heaven; but that the distinctions we observe, which God had established, being now removed, there were no longer any barriers to restrain the violent irruption.