The interpretation timeline
Revelation 22:2 Douay-Rheims

In the midst of the street thereof, and on both sides of the river, was the tree of life, bearing twelve fruits, yielding its fruits every month, and the leaves of the tree were for the healing of the nations.

A.D. 303 – 1871 7 witnesses

Patristic

before A.D. 750
303
A.D.
c. A.D. 250–303
“The river of life sets forth that the grace of spiritual doctrine flowed through the minds of the faithful, and that manifold flourishing forms of odours germinated therein. The tree of life on either bank sets forth the Advent of Christ, according to the flesh, who satisfied the peoples wasted with famine, that received life from One by the wood of the Cross, with the announcement of God's word.”
Source

Post-Reformation

c. 1650 – 1900
1771
A.D.
John Gill Reformed
1697–1771
“In the midst of the street of it,.... That is, of the city described in the preceding chapter, which shows that this vision belongs to that, and is a continuation of it, and which street was all of pure gold, Rev 21:21 and on either side of the river was there the tree of life; not that it stood either in the midst of the street of the city, which being a pavement of gold, a tree could not well stand there; nor on both sides of the river, which is impossible, unless the tree of life is put for many trees of the same kind, as in Ezekiel's vision, to which the allusion is; and so some were on one side of the river, and some on the other, as there; see Eze 47:7 or unless it can be thought that such a solution of the difficulty is sufficient, that the root of it was on one side, and the branches grew over to the other; though the words may be better rendered, and the difficulty will be removed, and the sense be clear, "between the street of it", the city, "and the river, on this side, and on that side"; that is, the street on one side, and the river on the other, was the tree of life; compare with this Joh 19:18. So the Jews say (e), that the tree of life is in the midst of paradise, and its body covers all the garden; and that there is in it five hundred thousand different tastes; and that there is no likeness and smell like it. By the tree of life is meant not the Gospel, nor godliness, nor eternal life, nor any other of the divine Persons, but Christ, who is the author of life, natural, spiritual, and eternal; See Gill on Rev 2:7 and its situation between the street of the city, where the saints commune and converse together, and the river of God's everlasting love, which in this state will appear in its fulness and glory, shows that Christ will be seen and enjoyed by all in the most delightful and comfortable manner that can be wished for: which bare twelve manner of fruits, and yielded her fruit every month; not one sort of fruit one month, and another sort another month, and so on, but twelve sorts every month; which is expressive of the fruits and spiritual blessings of grace from Christ, enjoyed by saints in the present state, and of that variety of happiness and pleasures to be had in this glorious state, and of the continuance of them; they being always ever fresh and new, and will be always sufficient for the twelve tribes of the true Israel of God, and for all that have embraced the doctrine of the twelve apostles of the Lamb; whose drink in this state will be the everlasting love of God, and whose food will be the fruit of the tree of life; both which they shall enjoy in great abundance: and the leaves of the tree were for the healing of the nations; not for the curing of diseases, or repairing of health; which in the present state of things is done by the application of the blood of Christ for the pardon of sin, which is a healing of diseases, and by the discoveries of the love of God; through the ministration of the Gospel, and the doctrines of it, which might be thought to be signified by leaves; for there will be no disease either of body or mind in this state; besides, the nations that will walk in the light of this city will be saved perfectly and completely, Rev 21:4 but these leaves will be for the preserving and continuing the health of the people of God in this state, as the tree of life in Eden's garden was for the preservation of the health and life of Adam, had he continued in a state of innocence; and it denotes that everything in Christ will contribute to the comfort, health, and happiness of the saints. The Jews interpret the passage in Eze 47:12 to which this refers, of future time, or the world to come (f); and speak of various trees and herbs of great fragrancy and medicinal virtues, which grow quite round on the sides of a laver that stands in paradise (g). (e) Yalkut Simeoni, par. 1. fol. 7. 1. (f) Shirhashirim Rabba, fol. 19. 1. (g) Sepher Avodah Hakkodesh, fol. 46. 1.”
Source
1832
A.D.
Adam Clarke Methodist
1762–1832
“In the midst of the street of it - That is, of the city which was described in the preceding chapter. The tree of life - An allusion to Gen 2:9. As this tree of life is stated to be in the streets of the city, and on each side of the river, tree must here be an enallage of the singular for the plural number, trees of life, or trees which yielded fruit by which life was preserved. The account in Ezekiel is this: "And by the river, upon the bank thereof, on this side and on that side, shall grow all trees for meat, whose leaf shall not fade - it shall bring forth new fruit, according to his months - and the fruit thereof shall be for meat, and the leaf thereof for medicine;" Eze 47:12. Twelve manner of fruits - Καρπους δωδεκα· Twelve fruits; that is, fruit twelve times in the year, as is immediately explained, yielded her fruit every month. As this was a great and spacious city, one fountain was not sufficient to provide water for it, therefore a river is mentioned; a great river, by which it was sufficiently watered. Some think that by this tree of life the Gospel is indicated; the twelve fruits are the twelve apostles; and the leaves are Gospel doctrines by which the nations - the Gentiles, are healed of the disease of sin. But this seems to be a fanciful interpretation.”
Source
1849
A.D.
1774–1849
“For the healing of the nations, or Gentiles, to signify the call of all Gentiles or nations to this heavenly happiness. (Witham)”
1863
A.D.
1871
A.D.
1871
“The harmonious unity of Scripture is herein exhibited. The Fathers compared it to a ring, an unbroken circle, returning into itself. Between the events of Genesis and those at the close of the Apocalypse, at least six thousand or seven thousand years intervene; and between Moses the first writer and John the last about one thousand five hundred years. How striking it is that, as in the beginning we found Adam and Eve, his bride, in innocence m Paradise, then tempted by the serpent, and driven from the tree of life, and from the pleasant waters of Eden, yet not without a promise of a Redeemer who should crush the serpent; so at the close, the old serpent cast out for ever by the second Adam, the Lord from heaven, who appears with His Bride, the Church, in a better Paradise, and amidst better waters (Rev 22:1): the tree of life also is there with all its healing properties, not guarded with a flaming sword, but open to all who overcome (Rev 2:7), and there is no more curse. street of it--that is, of the city. on either side of the river--ALFORD translates, "In the midst of the street of it (the city) and of the river, on one side and on the other" (for the second Greek, "enteuthen," A, B, and Syriac read, ekeithen: the sense is the same; compare Greek, Joh 19:18); thus the trees were on each side in the middle of the space between the street and the river. But from Eze 47:7, I prefer English Version. The antitype exceeds the type: in the first Paradise was only one tree of life; now there are "very many trees at the bank of the river, on the one side and on the other." To make good sense, supposing there to be but one tree, we should either, as MEDE, suppose that the Greek for street is a plain washed on both sides by the river (as the first Paradise was washed on one side by the Tigris, on the other by the Euphrates), and that in the midst of the plain, which itself is in the midst of the river's branches, stood the tree: in which case we may translate, "In the midst of the street (plain) itself, and of the river (having two branches flowing) on this and on that side, was there the tree of life." Or else with DURHAM suppose, the tree was in the midst of the river, and extending its branches to both banks. But compare Eze 47:12, the millennial type of the final Paradise; which shows that there are several trees of the one kind, all termed "the tree of life." Death reigns now because of sin; even in the millennial earth sin, and therefore death, though much limited, shall not altogether cease. But in the final and heavenly city on earth, sin and death shall utterly cease. yielded her fruit every month--Greek, "according to each month"; each month had its own proper fruit, just as different seasons are now marked by their own productions; only that then, unlike now, there shall be no season without its fruit, and there shall be an endless variety, answering to twelve, the number symbolical of the world-wide Church (compare Note, see on Rev 12:1; Rev 21:14). ARCHBISHOP WHATLEY thinks that the tree of life was among the trees of which Adam freely ate (Gen 2:9, Gen 2:16-17), and that his continuance in immortality was dependent on his continuing to eat of this tree; having forfeited it, he became liable to death; but still the effects of having eaten of it for a time showed themselves in the longevity of the patriarchs. God could undoubtedly endue a tree with special medicinal powers. But Gen 3:22 seems to imply, man had not yet taken of the tree, and that if he had, he would have lived for ever, which in his then fallen state would have been the greatest curse. leaves . . . for . . . healing-- (Eze 47:9, Eze 47:12). The leaves shall be the health-giving preventive securing the redeemed against, not healing them of, sicknesses, while "the fruit shall be for meat." In the millennium described in Eze. 47:1-23 and Rev 20:1-15, the Church shall give the Gospel-tree to the nations outside Israel and the Church, and so shall heal their spiritual malady; but in the final and perfect new Jerusalem here described, the state of all is eternally fixed, and no saving process goes on any longer (compare Rev 22:11). ALFORD utterly mistakes in speaking of "nations outside," and "dwelling on the renewed earth, organized under kings, and saved by the influences of the heavenly city" (!) Compare Rev 21:2, Rev. 21:10-27; the "nations" mentioned (Rev 21:24) are those which have long before, namely, in the millennium (Rev 11:15), become the Lord's and His Christ's.”
Source

Undated

date unknown
date
unknown
Glossa Ordinaria Medieval
“And on both sides. About the river, that is, in this life we have the tree of life, that is, the body and blood of Christ, in which we are refreshed; beyond the river, that is, in the time to come we shall have him present. Or by "about the river" let us understand the time before baptism, by "beyond", that which was after baptism, that we may denote the faithful both in the old and in the new law saved through Christ, which Moses signified, who led the sons of Israel up to the river Jordan, and Jesus the son of Nave, who from the river Jordan led them into the land of promise. The tree of life. As if he said: He himself gives the refreshment; he himself also gives to them those who would prepare those to whom he himself renders it. Fruits. That is, the prophets and apostles fructifying unto the faith of the Trinity through the four parts of the world. And the leaves of the tree. As if he said: And that Christ shall render fruit, this shall be thus, that the apostles, and after them others also, shall scatter the leaves of Christ himself.”
Source
Modern · 1953 →

The in-app commentary runs from the Fathers to the early-modern record, then stops — that's where the public-domain sources end, not where the reading does. For the modern reading, follow the sources directly.