Psalms 104:6

"The deep, like a garment, is its clothing." Whose? Is it perchance God's? But he had already said of His clothing, "Clothed with light as with a garment." I hear of God clothed in light, and that light, if we will, are we. What is, if we will? if we are no longer darkness. Therefore if God is clothed with light, whose clothing, again, is the deep? For an immense mass of waters is called the deep. All water, all the moist nature, and the substance everywhere shed abroad through the seas, and rivers, and hidden caves, is all together called by one name, the Deep. Therefore we understand the earth, of which he said, "He hath founded the earth." Of it I believe he said, "The deep, like a garment is its clothing." For the water is as it were the clothing of the earth, surrounding it and covering it. ...

Now, according to a Hebrew figure of speech, it is said of God in the eighteenth psalm that "he made darkness his secret place," to signify that those notions that should be worthily entertained of God are invisible and unknowable, because God conceals himself in darkness, as it were, from those who cannot endure the splendors of his knowledge or are incapable of looking at them, partly owing to the pollution of their understanding, which is clothed with the body of mortal lowliness, and partly owing to its feebler power of comprehending God. And in order that it may appear that the knowledge of God has rarely been vouchsafed to people and has been found in very few individuals, Moses is related to have entered into the darkness where God was. And again, with regard to Moses it is said, "Moses alone shall come near the Lord, but the rest shall not come near." And again, that the prophet may show the depth of the doctrines that relate to God and that are unattainable by those who do not possess the "Spirit that searches all things, even the deep things of God," he added, "The abyss like a garment is his covering." No, our Lord and Savior, the Logos of God, manifesting that the greatness of the knowledge of the Father, is appropriately comprehended and known preeminently by him alone, and in the second place by those whose minds are enlightened by the Logos and God, declares, "No one knows the Son but the Father; neither does any one know the Father but the Son, and he to whoever the Son will reveal him." For no one can worthily know the "uncreated" and firstborn of all created nature like the Father who begat him, nor any one the Father like the living Logos, and his Wisdom and Truth. […]

The deep, like a garment, is his clothing. As is written elsewhere: "And he made darkness his hiding-place," and again: "The judgments of the Lord are a great deep." He signifies the unspeakable governance of God, and that we cannot comprehend the wisdom of God. For just as we cannot gaze with these eyes into the deep, so neither can we gaze into the greatness nor into the wisdom of God. But according to the Hebrew we ought to understand "his clothing" in this way, that "of the earth" is to be supplied; so that the sense is that this very deep surrounds the whole earth — the thing they call the ocean. For around the whole earth there are waters, and the earth is like an island.

The waters shall stand above the mountains. Not, as some suppose, that the waters stand above the mountains because of winter and the rains; but the mountains were covered by the waters, and the earth did not appear. But according to the figurative interpretation, the waters are to be taken for doctrine, and the mountains for the saints.

Thou coverest it with the deep as with a garment,....