As to what some say that these things are so many that they cannot be compassed by the knowledge of God; they ought with like reason to maintain further that God cannot know all numbers which are certainly infinite. But infinity of number is not beyond the compass of His understanding, who is Himself infinite.
Therefore if whatever is compassed by knowledge, is bounded by the compass of him that has the knowledge, then is all infinity in a certain unspeakable way bounded by God, because it is not incomprehensible by His knowledge.
Reproduced in full. Translation: Oxford 1841 (Newman), public domain (Public domain).
Also cites: City of God, xii, 18