17 But, to resume: let us speak of the Unbegotten, the Begotten, and the Proceeding, if anyone likes to create names: for we shall have no fear of bodily conceptions attaching to Those who are not embodied, as the calumniators of the Godhead think. For the creature must be called God's, and this is for us a great thing, but God never. Otherwise I shall admit that God is a creature, if I become God, in the strict sense of the term. For this is the truth. If God, He is not a creature; for the creature ranks with us who are not Gods.
And if a creature, he is not God, for he had a beginning in time. And there was a time when he who had a beginning was not. And that of which non-existence was its prior condition, has not being in the strict sense of the term. And how can that, which strictly has not being, be God? Not one single one, then, of the Three is a creature, nor, what is worse, came into being for my sake; for in that case he would be not only a creature, but inferior in honour to us. For, if I am for the glory of God, and he is for my sake, as the tongs for the waggon, the saw for the door, I am his superior in causality. For in whatever degree God is superior to creatures, in the same degree is he, who came into being for my sake, inferior to me who exist for God's sake.
Source: Orations (New Advent)