Genesis 7:20

With the eye of my mind I gazed upon paradise. The summit of every mountain is lower than its summit, the crest of the flood reached only its foothills, these it kissed with reverence before turning back to rise above and subdue the peak of …

It is not without purpose that Scripture describes all this to us. Instead, its purpose is for us to learn that not only people, cattle, four-footed beasts and reptiles were drowned but also the birds of heaven and whatever inhabited the mountains, namely, animals and other wild creatures. Hence the text says, "The flood rose fifteen cubits above the mountains," for you to learn that the execution of the Lord's sentence had been effected. He said, remember, "After seven more days I will bring a deluge upon the earth and I will wipe off the face of the earth all the life I have made, from human beings to cattle, and from reptiles to birds of heaven." So Scripture narrates this not simply to teach us the flood level but that we may be able to understand along with this that there was absolutely nothing left standing—no wild beasts, no animals, no cattle—rather, everything was annihilated along with the human race. Since it was for their sake that all these creatures had been created, with the imminent destruction of the human beings it was fitting that these creatures too should meet their end. Then, after teaching us the great height reached by the flood waters and the fact that they rose a further fifteen cubits above the mountain peaks, it further adds out of fidelity to its characteristic precision, "There perished all flesh that moved on the earth—birds, animals, every reptile that moved on the earth, every human being—everything that had breath of life, everything on dry land: all perished." That was not an idle reference in the words "everything on dry land"; instead, its purpose was to teach us that while others perished, the just man with everyone in the ark alone was saved.

The water was fifteen cubits higher than the mountains which it covered. Indeed, seven and eight make fifteen; seven pertains to the rest of souls which is to be after death, since the Lord certainly rested in the tomb on the seventh Sabbath; but since …

Fifteen cubits upwards did the waters prevail,....

Fifteen cubits upward . . . and the mountains were covered--twenty-two and a half feet above the summits of the highest hills. The language is not consistent with the theory of a partial deluge.