Nicene and Post Nicene-Fathers, Vol. I:
The Confessions: Chapter X

Chapter X.—The Rashness of Those Who Inquire What God Did Before He Created Heaven and Earth.

12. Lo, are they not full of their ancient way, who say to us, “What was God doing before He made heaven and earth? For if,” say they, “He were unoccupied, and did nothing, why does He not for ever also, and from henceforth, cease from working, as in times past He did? For if any new motion has arisen in God, and a new will, to form a creature which He had never before formed, however can that be a true eternity where there ariseth a will which was not before? For the will of God is not a creature, but before the creature; because nothing could be created unless the will of the Creator were before it. The will of God, therefore, pertaineth to His very Substance. But if anything hath arisen in the Substance of God which was not before, that Substance is not truly called eternal. But if it was the eternal will of God that the creature should be, why was not the creature also from eternity?”