4 Since, therefore, as the mercy of God is multiplied, men and beasts are saved by Him, have not men something else which God as Creator bestows on them, which He bestows not on the beasts? Is there no distinction between the living creature made after the image of God, and the living creature made subject to the image of God? Clearly there is: beyond that salvation common to us with the dumb animals, there is what God bestows on us, but not on them. What is this? Follow on in the same psalm: “But the sons of men shall hope under the covert of Your wings.”
Having now a salvation in common with their cattle, “the sons of men shall hope under the covert of Your wings.” They have one salvation in fact, another in hope. This salvation which is at present is common to men and cattle; but there is another which men hope for; and which they who hope for receive, they who despair of receive not. For it says, “The sons of men shall hope under covert of Your wings.” And they that perseveringly hope are protected by You, lest they be cast down from their hope by the devil: “Under covert of Your wings they shall hope.”
If they shall hope, what shall they hope for, but for what the cattle shall not have? “They shall be fully drunk with the fatness of Your house; and from the torrent of Your pleasure You shall give them drink.” What sort of wine is that with which it is laudable to be drunk? What sort of wine is that which disturbs not the mind, but directs it? What sort of wine is that which makes perpetually sane, and makes not insane by drinking? “They shall be fully drunk.” How? “With the fatness of Your house; and from the torrent of Your pleasure You shall give them drink.”
How so? “Because with You is the fountain of life.” The very fountain of life walked on the earth, the same who said, “Whoso thirsts, let him come unto me.” Behold the fountain! But we begin to speak about the light, and to handle the question laid down from the Gospel concerning the light. For we read how the Lord said, “I am the light of the world.” Thence arose a question, lest any one, carnally understanding this, should fancy this light to mean the sun: we came thence to the psalm, which having considered, we found meanwhile that the Lord is the fountain of life.
Drink and live. “With You,” it says, “is the fountain of life;” therefore, “under the shadow of Your wings the sons of men hope,” seeking to be full drunk with this fountain. But we were speaking of the Light. Follow on, then; for the prophet, having said, “With You is the fountain of life,” went on to add, “In Your light shall we see light,”— God of God, Light of Light. By this Light the sun's light was made; and the Light which made the sun, under which He also made us, was made under the sun for our sake. That Light which made the sun, was made, I say, under the sun for our sake. Do not despise the cloud of the flesh; with that cloud it is covered, not to be obscured, but to be moderated.
Source: Tractates on the Gospel of John (New Advent)