John Calvin Commentary Genesis 1:20

"And God said, Let the waters swarm with swarms of living creatures, and let birds fly above the earth in the open firmament of heaven." — Genesis 1:20 (ASV)

Let the waters bring forth... the moving creature. On the fifth day the birds and fishes are created. The blessing of God is added, so that they might produce their own offspring. Here is a different kind of propagation from that in herbs and trees: for in those, the power of bearing fruit is in the plants, and that of germinating is in the seed; but here, generation takes place.

It seems, however, hardly consistent with reason that he declares birds to have come from the waters; and therefore, this is seized upon by critical men as an opportunity for slander. But even if no other reason were apparent than that it so pleased God, would it not be fitting for us to acquiesce in His judgment?

Why should it not be lawful for Him, who created the world out of nothing, to bring forth birds from water? And what greater absurdity, I pray, is there in the origin of birds from water, than in that of light from darkness? Therefore, let those who so arrogantly assail their Creator expect the Judge who will reduce them to nothing.

Nevertheless, if we must use physical reasoning in this debate, we know that the water has a greater affinity with the air than the earth does. But we should rather listen to Moses as our teacher, who would lead us to marvel at God by considering His works. And truly, the Lord, although He is the Author of nature, by no means followed nature as His guide in the creation of the world, but rather chose to display such demonstrations of His power as would compel us to wonder.