The Tree of Life has been a topic of special interest to me since I made the connection with the lignum vitae (The Tree That Grows in Heaven.) Here is Jerome’s linkage of Psalm 1 with the other allusions to the tree, from his Homilies on the Psalms (from here):
“He is like a tree planted near running water, that yields its fruit in due season, and whose leaves never fade” There are many who interpret these words very simply to mean that just as a tree, if planted near water, will take root and grow and not wither away because it has enough moisture, so in like manner one who meditates on the law of God will derive strength and life from his meditation. This is their simple interpretation. But we shall combine spiritual things with spiritual things and read of the tree of life that was planted in Paradise, the tree of life and the tree of the knowledge of good and evil. This tree of life was planted in the Garden of Eden and in Eden there rose a river that separated into four branches. Likewise we read in Solomon – if one accepts that book as Solomon’s, for he speaks there of wisdom (Christ the power of God and the wisdom of God) – so then, as I was saying, where Solomon says: “She is a tree of life to those who grasp her” he is speaking of wisdom. Now, if wisdom is the tree of life. Wisdom itself, indeed, is Christ. You understand now that the man who is blessed and holy is compared to this tree, that is, he is compared to Wisdom. Consequently, you see, too that the just man, that blessed man who has not followed in the counsel of the wicked-who has not done that but has done this-is like the tree that is planted near running water, is. in other words, like Christ, inasmuch as He “raised us up together, and seated us together in heaven” You see, then, that we shall reign together with Christ in heaven; you see, too, that because this tree has been planted in the Garden of Eden, we have all been planted there together with Him.
“He is like a tree planted near running water” Indeed, it is from that fountain-head that all rivers take their rise. “That yields its fruit in due season” This tree does not yield fruit in every season, but in the proper season. This is the tree that does not yield its fruit in the present day, but in the future, that is, on the Day of Judgement. This is the tree that bears blossoms now, that buds forth now, and promises fruits for the future. This tree bears twofold: it produces fruit and it produces foliage. The fruit that it bears contains the meaning of Scripture; the leaves, only the words. The fruit is in the meaning; the leaves are in the words. For that reason, whoever reads Sacred Scripture, if he reads merely as the Jews read, grasps only the words. If he rends with true spiritual insight, he gathers the fruit.
“And whose leaves never fade” The leaves of this tree are by no means useless. Even if one understands Holy Writ only as history, he has something useful for his soul. We read in the Apocalypse of John (a book which, although rejected in these regions,we ought nevertheless to know, because it is accepted and held as canonical throughout die West, and in other Phoenician provinces, and in Egypt, for the ancient churchmen, including Irenaeus, Polycarp, Dionysius, and other Roman expounders of Sacred Scripture, among whom is holy Cyprian, accept and interpret it): “Behold, I saw a throne set up, and one Lamb and a tree alongside a river, and on both sides of the river was that tree.” This means that the tree was both on this side and on that side of the river. “And this tree” he says, “bore fruit and was yielding its twelve fruits for the year according to each month. And it had leaves, too, and the leaves for the healing of the nations”.
“I saw” he says, “a single throne set up” We believe in the Father, and the Son, and the Holy Spirit, that is true, and that they are a Trinity; nevertheless the kingship is one. ”I saw a single throne set up, and I saw a single Lamb standing in the presence of the throne” This refers to the Incarnation of the Saviour. Scripture says: “Behold the lamb of God, who takes away the sin of the world!” – “And there was a fountain of water corning forth from beneath the middle of the throne.” Notice that it is from the midst of the throne that there issues forth a river of graces. That river does not issue forth from the throne unless the Lamb is standing before it, for unless we believe in the Incarnation of Christ, we do not receive those graces.
A tree, he says, one lofty tree had been set up. He did not say trees, but only one tree. If there is but one tree, how can it be on both sides of the river? If he had said, I saw trees, it would have been possible for some trees to be on one side of the river and other trees on the other side. Actually, one tree is said to be on both sides of the river. One river comes forth from the throne of God-the grace of the Holy Spirit-and this grace of the Holy Spirit is found in the river of the Sacred Scriptures. This river, moreover, has two banks, the Old Testament and the New Testament, and the tree planted on both sides is Christ. During the year, this tree yields twelve fruits, one for each month, but we are unable to receive the fruits except through the apostles. If one approaches the tree through the apostles, he must receive the fruit; he gathers the fruit from the Sacred Scriptures; he grasps the divine meaning abiding within the words. If, therefore, one comes to this tree through the apostles, he gathers its fruit just as we have said. If, indeed, he cannot pluck the fruit, it is because he is still too weak; he is not yet a disciple, but belongs to the throng; he is an outsider, a stranger from the nations. Because he cannot pluck the fruit, he plucks only words, the leaves for the healing of the nations, for it is written: “and the leaves are for the healing of the nations”. One who belongs to the nations, who is not a disciple, who is as yet only one or the crowd, gathers only leaves from the tree; he receives from Scripture plain words for a healing remedy. Briefly, then, the Scripture says; “and the leaves of the tree are for the healing of the nations”; in other words, the leaves are medicine. Why have we digressed on the Apocalypse? Simply because of that tree “that yields its fruit in due season, and whose leaves never fade. Whatever he does prospers.”
We have discussed the happiness of the just man. We spoke of his reward. Because of the three things he did not do and the two things he did do, he was compared to the tree in the Garden of Eden, to Christ, who is Wisdom. We have said all this about the holy man.