Now concerning the food and drink of the heavenly citizens, we read these words in the Apocalypse: And he showed me a river of water of life, bright as crystal, proceeding from the throne of God and of the Lamb. In the midst of the street thereof, and on either side of the river, was the tree of life, bearing twelve fruits, yielding its fruit every month; and the leaves of the tree were for the healing of the nations (Rev. 22:1-2). I fear that those who hear these things may marvel at the frugality of the fare of the heavenly citizens, and suppose that more and better things are to be had in this our pilgrimage: for here we hear of nothing but the fruits of a single tree for food, and the water of a river for drink. But let those who say this remember that in the earthly paradise, where without doubt the fare would have been better than in this exile, Adam was granted for food nothing but fruits and herbs, and water for drink: and yet those fruits, and those herbs, and those waters were better than all the foods and all the wines of this life, though far, far inferior to the tree of life and the living water of the heavenly paradise (Gen. 2). In this vale of miseries all men are sick, and their sense of taste is corrupted by a certain bitterness; therefore, to take away the nausea, they have devised a variety of foods: yet that variety of food so lessens the nausea that it increases the disease. In the earthly paradise all men would have been wholly sound; and such was the healthfulness and sweetness of those fruits and that water, that they could have nourished men perfectly and preserved them in health with incredible delight; to say nothing of the fact that, without labor and sweat, they would have had food and drink abundantly at hand. But whatever may be said of the earthly paradise, the living water and the tree of life in the city of God are not food and drink common to men and beasts, as are the waters and fruits of this pilgrimage: they are so choice, so great, so divine, that the Prophet sings: They shall be inebriated with the plenty of Thy house, and Thou shalt make them drink of the torrent of Thy pleasure (Ps. 35:9). Nor are those foods and drinks corporeal things, but spiritual and divine. The living water is wisdom, of which we read: She shall give him the water of wholesome wisdom to drink (Sir. 15:3). And the tree of life is that bread of which the same book says: She shall feed him with the bread of life and understanding. For as St. Augustine teaches, in corporeal things food is one thing and drink is another; but in spiritual things the same thing is food and drink — that is, wisdom, or understanding, or intelligence, which here mean the same thing: it is food because it nourishes, and drink because it quenches thirst. Still, by the living water wisdom might also be understood, and by the tree of life, charity; for we have it from the same John in his first Epistle: He that loveth not, abideth in death (1 John 3:14); and: We know that we have passed from death to life, because we love the brethren (1 John 3:14). And truly both to understand and to love are vital acts. Therefore the drink of the blessed in the city of God is to drink of the living river that springs from the fountain of life, who is God: that is, the fruition of a participation in that wisdom by which God is wise, which is the highest, most exalted, and unutterable. And the food of the same blessed is to eat of the tree of life — that is, the fruition of a participation in that ineffable love by which goodness itself, clearly beheld, can be loved, and by which God loves Himself, who is the infinite good and the fountain of all goodness. What these things are, we can in some measure surmise; we cannot understand them, nor shall we be able to, until we come to that city.
But what St. John says — that the tree is on either side of the river and yields its fruit every month — is to be understood metaphorically, that he might in some manner, through the likeness of corporeal things, express spiritual things: a tree of supreme goodness and fruitfulness. To this end he described a tree standing on the bank of the river, which, both by its own goodness and by continual watering, brings forth its fruit every month, not once a year as other trees are wont. Nor does he mean to signify that there is only one tree, but many of the same kind, planted on either side of the river that flows through the midst of the city, so that between one tree and another there is no great space; and in this way the whole city can enjoy both the course of the water and the fruit of the trees. The goodness of the tree is signified in the name tree of life; its fruitfulness is shown in this, that it bears new fruits every month. Whence it comes that the citizens of that city always have fruits both fresh and ripe: fresh from the present month, ripe from the month just past; never withered, never dry, never insipid. All of which signifies that the food and drink of the blessed — that is, the wisdom by which they perfectly understand God, and the charity by which they perfectly love Him — is the best, and never fails.
What the same blessed Evangelist adds concerning the leaves of that tree — that they are for the healing of the nations — seems to signify this: that to us in this exile the very fruits of the tree of life are never sent, yet certain leaves are sent, which, although they do not bring us eternal life itself, are nonetheless useful for the healing of our diseases: the concupiscence of the eyes, the pride of life, and other vices of the same kind, from which we are all sick, some gravely and some lightly. These leaves are the divine words brought down to us from heaven — that is, from divine revelation — through the Prophets and Apostles. O how good a fragrance those leaves breathe forth, if a man have the Spirit of the Lord! Read the Prophets, read the Psalmist, read the Gospels, read the Apostles — Peter, Paul, John, James, Jude: all these leaves breathe humility, the charity of God, virginity, things of which there is no mention among the philosophers. Nor should this seem strange; for the former are leaves from the trees of paradise, the latter from the trees of the mountains of the earth.
Therefore, Christian soul, diligently gather these leaves; make for yourself of them a daily medicine; and from the leaves form a conjecture of the fruits. And despising the husks of swine, sigh ardently for those fruits of eternal life which are on high; think upon them; let the memory of them abide with you always, until their presence be granted.