And God said,
Let the waters bring forth abundantly the moving creature that has life, and fowl that may fly above the earth in the open firmament of heaven.
All Commentaries on Genesis 1:20 Go To Genesis 1
Tertullian of Carthage
Therefore God, when producing other things out of things which had been already made, indicates them by the prophet, and tells us what He has produced from such and such a source (although we might ourselves suppose them to be derived from some source or other, short of nothing; since there had already been created certain things, from which they might easily seem to have been made). [Against Hermagenes 22]