5 But though we have said that angels eat, do not fancy, brethren, that this is done with teeth. For if you think so, God, of whom the angels eat, is as it were torn in pieces. Who tears righteousness in pieces? But still, some one asks me, And who is it that can eat righteousness? Well, how is it said, “Blessed are they that hunger and thirst after righteousness, for they shall be filled”? The food which you eat carnally perishes, in order to refresh you; to repair your waste it is consumed: eat righteousness; and while you are refreshed, it continues entire.
Just as by seeing this corporeal light, these eyes of ours are refreshed, and yet it is a corporeal thing that is seen by corporeal eyes. Many there have been, when too long in darkness, whose eyesight is weakened by fasting, as it were, from light. The eyes, deprived of their food (for they feed on light), become wearied by fasting, and weakened, so that they cannot bear to see the light by which they are refreshed; and if the light is too long absent, they are quenched, and the very sense of sight dies as it were in them.
What then? Does the light become less, because so many eyes are daily fed by it? Your eyes are refreshed, and the light remains entire. As God was able to show this in the case of corporeal light to corporeal eyes, does He not show that other light to clean hearts as unwearied, continuing entire, and in no respect failing? What light? “In the beginning was the Word, and the Word was with God.” Let us see if this is light. “For with You is the fountain of light, and in Your light shall we see light.”
On earth, fountain is one thing, light another. When thirsting, you seek a fountain, and to get to the fountain you seek light; and if it is not day, you light a lamp to get to the fountain. That fountain is the very light: to the thirsting a fountain, to the blind a light. Let the eyes be opened to see the light, let the lips of the heart be opened to drink of the fountain; that which you drink, you see, you hear, God becomes all to you; for He is to you the whole of these things which you love.
If you regard things visible, neither is God bread, nor is God water, nor is God this light, nor is He garment nor house. For all these are things visible, and single separate things. What bread is, water is not; and what a garment is, a house is not; and what these things are, God is not, for they are visible things. God is all this to you: if you hunger He is bread to you; if you thirst He is water to you; if you are in darkness, He is light to you: for He remains incorruptible.
If you are naked, He is a garment of immortality to you, when this corruptible shall put on incorruption, and this mortal shall put on immortality. All things can be said of God, and nothing is worthily said of God. Nothing is wider than this poverty of expression. You seek a fitting name for Him, you can not find it; you seek to speak of Him in any way soever, you find that He is all. What likeness have the lamb and the lion? Both is said of Christ. “Behold the Lamb of God!” How a lion? “The Lion of the tribe of Judah has prevailed.”
Source: Tractates on the Gospel of John (New Advent)