Theophilus of Antioch, To Autolycus 13

But to start from earthly things below and call the making of created things human, lowly, and very weak in its conception toward God — that is what it is. A human, being low, begins building from the ground, yet cannot achieve order and make a roof unless he first lays a foundation. God's power, however, is shown in this: he first makes what comes to be from non‑being, and does so as he wishes. What is impossible for humans is possible for God. Therefore the prophet first spoke of the heaven's making as holding the character of a roof, saying, 'In the beginning God made the heaven' — that is, through the beginning the heaven came to be, as we have already shown (Genesis 1:1). He calls earth powerful ground and foundation; abyss is the mass of the waters; darkness exists because the heaven God made covered the waters and the earth like a lid. Spirit is what was brought upon the water, which God gave to quicken creation, just as a soul to a human — the fine mingling with the fine (for spirit is fine and water is fine) — so that the spirit may nourish the water, and the water together with the spirit may nourish creation, passing through everywhere. The one spirit, bearing a likeness of light, mediated between the water and the heaven, so that in some way darkness might not share with the heaven, which is nearer to God, before God said, 'Let light come to be.' Just as the heaven, being a vault, held the matter like a lump. And another prophet, named Isaiah, also spoke of the heaven, saying, 'God is the one who made the heaven like a vault and stretched it out like a tent to dwell' (Isaiah 40:22). God's arrangement — that is, his Word — shining like a lamp in an enclosed room, illuminated the region under heaven, having made it apart from the world. God called the light day and the darkness night; for a human would not have known to call the light day or the darkness night, nor anything else, had he not received the naming from the God who made them.

In the first premise of the history and genesis of the world, holy Scripture spoke not of this firmament but of another heaven, invisible to us, after which this visible heaven is called firmament — the one upon which half the water was taken up, so that it might serve humanity for rains, showers, and dews. The other half of the water was left on the earth for rivers, springs, and seas. While the water still held the earth, especially the hollow places, God through his Word made the water gather into one gathering and the dry land become visible, though it had previously been invisible. The earth, now visible, still existed unprepared. God therefore prepared and adorned it with all kinds of grasses, seeds, and plants.