John 12:45
“He that sees Me, sees Him that sent Me.”
What then! Is God a body? By no means. The “seeing” of which He here speaks is that of the mind, thence showing the Consubstantiality. And what is, “He that believes in Me”? It is as though one should say, “He that takes water from the river, takes it not from the river but from the fountain”; or rather this image is too weak, when compared with the matter before us.
Source: Homilies on the Gospel of John (New Advent)