Genesis 1:21

21.And God created A question here arises out of the word created. For we have before contended, that because the world was created, it was made out of nothing; but now Moses says that things formed from other matter were created. They who truly and properly assert that the fishes were created because the waters were in no way sufficient or suitable for their production, only resort to a subterfuge: for, in the meantime, the fact would remain that the material of which they were made existed before; which, in strict propriety, the word created does not admit. I therefore do not restrict the creation here spoken of to the work of the fifth day, but rather suppose it to refer to that shapeless and confused mass, which was as the fountain of the whole world. (76) God then, it is said, created whales (balaenas) and other fishes, not that the beginning of their creation is to be reckoned from the moment in which they receive their form; but because they are comprehended in the universal matter which was made out of nothing. So that, with respect to species, form only was then added to them; but creation is nevertheless a term truly used respecting both the whole and the parts. The word commonly rendered whales (cetos vel cete) might in my judgment be not improperly translated thynnus or tunny fish, as corresponding with the Hebrew word thaninim. (77)

When he says that “the waters brought forth,” (78) he proceeds to commend the efficacy of the word, which the waters hear so promptly, that, though lifeless in themselves, they suddenly teem with a living offspring, yet the language of Moses expresses more; namely, that fishes innumerable are daily produced from the waters, because that word of God, by which he once commanded it, is continually in force.