Genesis 1:29

The historical meaning, at least, of this sentence indicates clearly that originally God permitted the use of foods from vegetation, that is, vegetables and the fruits of trees. But the opportunity of eating flesh is given to men later when a covenant was made with Noah after the flood.

Man’s first food was solely fruit and produce from trees. Man’s guilt subsequently introduced the use of bread. The posture of his body shows forth the state of his conscience. As long as man’s conscience did not reproach him, innocence raised him up toward the heavens to pluck his food from the trees. Once sin had been committed, it bowed man down to the soil of the earth to get grain. Still later the use of meat was added.

We note, however, many wild beasts do not eat fruit. What fruit does the panther eat? What fruit makes the lion strong? But nevertheless these creatures, when submitting to the laws of nature, ate fruits. And likewise when the [first] man changed his way of life and voided the limits set upon him, the Lord, after the flood, knowing humans were wasteful, allowed them to use all foods: “Eat every food as if it were edible plants.” Since [humans] were allowed this [concession], the other animals [also] received the liberty to eat. So the lion is [now] a meat-eater, and the vulture looks for carrion.But vultures were not yet circling above the earth to find carrion when the animals originated; nothing created nor imagined had yet died in order to be food for the vultures. Nature had not yet been divided; everything was completely fresh. Hunters did not capture prey, since people did not yet practice this. The beasts did not yet tear apart prey, since they were not meat eaters yet.… So was the first creation, and to this creation will be restored after this [age]. Humans will return to their original creation, rejecting hostility, a life encumbered with care, the slavery of the world to daily worries. Once they have renounced all this, they will return to that utopian life which is not enslaved to the passions of the flesh, which is freedom, the closeness to God, a partaker of the life of the angels.

I myself hold with those who, considering the words, "Male and female he created them, saying, 'Increase and multiply and fill the earth,' " interpret them as referring to visible and bodily sex. This is clear, in view of what follows: "And God said, 'Behold, I have given you every plant yielding seed which is upon the face of all the earth, and every tree with seed in its fruit; you shall have them for food. And to every beast of the earth, and to every bird of the air, and to everything that creeps on the earth, everything that has the breath of life, I have given every green plant for food.' " Note that both male and female used the food for the body that the other animals used. They received fitting sustenance from it. This was necessary for the animal body lest it suffer from hunger. But it was received in a certain immortal way and from the tree of life, lest they die of old age. I would never believe that, in a place of such great happiness, either the flesh lusted against the spirit or the spirit against the flesh, and there was no internal peace.… We conclude, therefore, that there was no carnal concupiscence in that place. Such was the manner of life that all necessities were taken care of by the proper functions of the members, without arousing lust.

And God said: Behold, I have given you every herb bearing seed upon the earth, and all the trees which have in themselves the seed of their own kind, to be your food, and to all the beasts of the earth and every bird, and to all that move upon the earth, and in which there is a living soul, that you may have them to eat: It is now clear that before man's guilt the earth produced nothing harmful, no poisonous herb, no sterile tree, since it was clearly said that every herb and all trees were given to men and the birds, and to all the beasts of the earth for food, it is evident that even the birds did not live by snatching weak wings, nor did the wolf plot ambushes around the folds, nor was dust the snake's bread, but all ate in concord the green herbs and the fruits of the trees. Certainly among these must arise the question of how man was made immortal above other creatures, and nevertheless received common earthly nourishment with them. In which we must see that there is one kind of immortality of the flesh which we received in Adam's first state, and another which we hope to receive in the resurrection through Christ. Thus, he was made immortal in such a way that he could not die if he did not sin; but if he did sin, he would die. Thus the children of the resurrection will be immortal, when they will be equal to the angels of God, so that they will neither die anymore, nor be able to sin. Therefore our flesh after the resurrection will need no nourishment of food, as it will not be subject to deficiency from hunger, or weariness, or any other kind of weakness. But Adam's flesh before sin was created immortal in such a way that, helped by the supports of temporal nourishment, it existed free from death and pain, until, having been brought to that age which pleased the Creator through bodily growths; then having created much progeny of this kind, by the command of God, it would also partake of the tree of life, from which becoming perfectly immortal, it would no longer need the sustenance of bodily food. Thus, therefore, the flesh of the first humans is created immortal and incorruptible, so that they might retain the same immortality and incorruptibility through obedience to God's commandments; among which commandments was also this, that they should eat of the allowed trees of paradise, but refrain from the consumption of the forbidden one, preserving the gifts of immortality granted to them by the consumption of these, and in the touch of that find the ruin of death. Thus indeed our flesh will be incorruptible and immortal at the end; so that, like angelic splendour, it may remain always in the same state, unable to need bodily foods, since in the spiritual life there will be no need of them. For the fact that angels are read to have eaten with the patriarchs was done not out of need but out of kindness, so that by doing these things they might more sweetly adapt to the men to whom they appeared. The Lord also after the resurrection ate with the disciples, not because he needed nourishment but to show that he had indeed received true flesh after death.