2 And God said “Let there be a firmament in the midst of the waters, and let it divide the waters from the waters.” Yesterday we heard God's decree, “Let there be light.” Today it is, “Let there be a firmament.” There appears to be something more in this. The word is not limited to a simple command. It lays down the reason necessitating the structure of the firmament: it is, it is said, to separate the waters from the waters. And first let us ask how God speaks? Is it in our manner?
Does His intelligence receive an impression from objects, and, after having conceived them, make them known by particular signs appropriate to each of them? Has He consequently recourse to the organs of voice to convey His thoughts? Is He obliged to strike the air by the articulate movements of the voice, to unveil the thought hidden in His heart? Would it not seem like an idle fable to say that God should need such a circuitous method to manifest His thoughts? And is it not more conformable with true religion to say, that the divine will and the first impetus of divine intelligence are the Word of God?
It is He whom Scripture vaguely represents, to show us that God has not only wished to create the world, but to create it with the help of a co-operator. Scripture might continue the history as it is begun: In the beginning God created the heaven and the earth; afterwards He created light, then He created the firmament. But, by making God command and speak, the Scripture tacitly shows us Him to Whom this order and these words are addressed. It is not that it grudges us the knowledge of the truth, but that it may kindle our desire by showing us some trace and indication of the mystery.
We seize with delight, and carefully keep, the fruit of laborious efforts, while a possession easily attained is despised. Such is the road and the course which Scripture follows to lead us to the idea of the Only begotten. And certainly, God's immaterial nature had no need of the material language of voice, since His very thoughts could be transmitted to His fellow-worker. What need then of speech, for those Who by thought alone could communicate their counsels to each other?
Voice was made for hearing, and hearing for voice. Where there is neither air, nor tongue, nor ear, nor that winding canal which carries sounds to the seat of sensation in the head, there is no need for words: thoughts of the soul are sufficient to transmit the will. As I said then, this language is only a wise and ingenious contrivance to set our minds seeking the Person to whom the words are addressed.
Source: Nine Homilies of Hexaemeron (New Advent)