Bede : 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 He rose from the dead after the Sabbath, that is, on the eighth day, the number eight very rightly indicates the time of our resurrection. Therefore, the water surpassed the high mountains by fifteen cubits, that is, seven and eight, because the faith of the Church, sanctified by the fountain of the saving washing, surpasses in the hope of future rest and immortality all the arrogance of carnal philosophy, which indeed knows how to subtly dispute about the creation of the world, but knows nothing to say about the Creator of the world and the life of the saints that is above the world. — Commentary on Genesis (Hexaemeron) John Chrysostom : 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. — HOMILIES ON Genesis 25.20 Augustine of Hippo : FROM THE RISE OF WATER ABOVE THE MOUNTAINS DURING THE DELUGE. — There is a difficulty regarding the height of the mountains, recalling the legend of the Olympus. (Cf. LUCANUS, Phars. 2, 271-273; cf. anche De civ. Dei 15, 27; De Gen. ad l. imp. 14, 44; De Gen. c. Man. 1, 15, 24.) It is written that the water exceeded fifteen cubits of the summit of the highest mountain. But if the earth has been able to invade the space of this tranquil region, inaccessible to winds and storms, why could not the water, rising, have reached this point? [ — QUESTIONS ON GENESIS, Q. 9 (tr. J. Litteral, draft)