9 But as far as concerns the separation of the waters I am obliged to contest the opinion of certain writers in the Church who, under the shadow of high and sublime conceptions, have launched out into metaphor, and have only seen in the waters a figure to denote spiritual and incorporeal powers. In the higher regions, above the firmament, dwell the better; in the lower regions, earth and matter are the dwelling place of the malignant. So, say they, God is praised by the waters that are above the heaven, that is to say, by the good powers, the purity of whose soul makes them worthy to sing the praises of God.
And the waters which are under the heaven represent the wicked spirits, who from their natural height have fallen into the abyss of evil. Turbulent, seditious, agitated by the tumultuous waves of passion, they have received the name of sea, because of the instability and the inconstancy of their movements. Let us reject these theories as dreams and old women's tales. Let us understand that by water water is meant; for the dividing of the waters by the firmament let us accept the reason which has been given us.
Although, however, waters above the heaven are invited to give glory to the Lord of the Universe, do not let us think of them as intelligent beings; the heavens are not alive because they “declare the glory of God,” nor the firmament a sensible being because it “shows His handiwork.” And if they tell you that the heavens mean contemplative powers, and the firmament active powers which produce good, we admire the theory as ingenious without being able to acknowledge the truth of it.
For thus dew, the frost, cold and heat, which in Daniel are ordered to praise the Creator of all things, will be intelligent and invisible natures. But this is only a figure, accepted as such by enlightened minds, to complete the glory of the Creator. Besides, the waters above the heavens, these waters privileged by the virtue which they possess in themselves, are not the only waters to celebrate the praises of God. “Praise the Lord from the earth, you dragons and all deeps.” Thus the singer of the Psalms does not reject the deeps which our inventors of allegories rank in the divisions of evil; he admits them to the universal choir of creation, and the deeps sing in their language a harmonious hymn to the glory of the Creator.
Source: Nine Homilies of Hexaemeron (New Advent)