Answer me this question. Is there only one God? You answer, “Yes, there is only one Law-giver.” Why, then, does He command contrary things? The cherubim are not outside of creation; why, then, does He allow cherubim carved by the hand of man to overshadow the mercy-scat? Is it not evident that as it is impossible to make an image of God, who is uncircumscribed and impassible, or of one like to God, creation should not be worshipped as God. He allows the image of the cherubim who are circumscribed, and prostrate in adoration before the divine throne, to be made, and thus prostrate to overshadow the mercy-seat. It was fitting that the image of the heavenly choirs should overshadow the divine mysteries.
St. John Damascene
Apology Against Those Who Decry Holy Images
Part I