Gregory the Great

(xviii. Moral. c. 54. [88] rec. 28) It is plainly given us to understand here, that while we are in this mortal state, we can see God only through the medium of certain images, not in the reality of His own nature. A soul influenced by the grace of the Spirit may see God through certain figures, but cannot penetrate into his absolute essence. And hence it is that Jacob, who testifies that he saw God, saw nothing but an Angel: and that Moses, who talked with God face to face, says, Shew me Thy way, that I may know Thee: (Exod. 33:13) meaning that he ardently desired to see in the brightness of His own infinite Nature, Him Whom he had only as yet seen reflected in images.