The interpretation timeline
Revelation 21:17 Douay-Rheims

And he measured the wall thereof an hundred and forty-four cubits, the measure of a man, which is of an angel.

A.D. 303 – 1871 6 witnesses

Patristic

before A.D. 750
303
A.D.
c. A.D. 250–303
“The city which he says is squared, he says also is resplendent with gold and precious stones, and has a sacred street, and a river through the midst of it, and the tree of life on either side, bearing twelve manner of fruits throughout the twelve months; and that the light of the sun is not there, because the Lamb is the light of it; and that its gates were of single pearls; and that there were three gates on each of the four sides, and that they could not be shut. I say, in respect of the square city, he shows forth the united multitude of the saints, in whom the faith could by no means waver. As Noah is commanded to make the ark of squared beams, that it might resist the force of the deluge, by the precious stones he sets forth the holy men who cannot waver in persecution, who could not be moved either by the tempest of persecutors, or be dissolved from the true faith by the force of the rain, because they are associated of pure gold, of whom the city of the great King is adorned. Moreover, the streets set forth their hearts purified from all uncleanness, transparent with glowing light, that the Lord may justly walk up and down in them.”
Source

Post-Reformation

c. 1650 – 1900
1771
A.D.
John Gill Reformed
1697–1771
“And he measured the wall thereof, an hundred and forty and four cubits,.... The root of which is twelve, for twelve times twelve is a hundred and forty four; which number is mystical and apostolical, and suited to the perfect state of this church: hence twelve gates, and twelve angels at them, and the names of the twelve tribes on them, and twelve foundations of the wall, and twelve thousand furlongs, the measure of the city. According to the measure of a man, that is, of the angel; who talked with John, and measured the city, gates, and wall, and who appeared in the form of a man; and his reed might be, as some have supposed, the length of a man, six cubits, or six feet, as in Eze 40:5 and may denote that this business requires the utmost wisdom and understanding of a man, and even of an angel, to look into, and find out; see Rev 13:18 and also may signify the angelic state of the saints at this time, when the children of the resurrection will be like the angels of God, for immortality and glory.”
Source
1832
A.D.
Adam Clarke Methodist
1762–1832
“The wall - a hundred and forty and four cubits - This is twelve, the number of the apostles, multiplied by itself: for twelve times twelve make one hundred and forty-four. The measure of a man, that is, of the angel - The cubit, so called from cubitus, the elbow, is the measure from the tip of the elbow to the tip of the middle finger, and is generally reckoned at one foot and a half, or eighteen inches; though it appears, from some measurements at the pyramids of Egypt, that the cubit was, at least in some cases, twenty-one inches. By the cubit of a man we may here understand the ordinary cubit, and that this was the angel's cubit who appeared in the form of a man. Or suppose we understand the height of the man as being here intended, and that this was the length of the measuring rod. Now allowing this height and rod to be six feet, and that this was intended to have some kind of symbolical reference to the twelve tribes, mentioned Rev 21:12, represented by the twelve gates; and to the twelve apostles, represented by the twelve thresholds or foundations; then twenty-four, the number of the tribes and apostles, multiplied by six, make precisely the number one hundred and forty-four.”
Source
1849
A.D.
1774–1849
“The measure of a man, which is of an Angel. [2] This seems, without doubt, the sense of it. (Witham)”
1871
A.D.
1871
“hundred . . . forty . . . four cubits--twelve times twelve: the Church-number squared. The wall is far beneath the height of the city. measure of a man, that is, of the angel--The ordinary measure used by men is the measure here used by the angel, distinct from "the measure of the sanctuary." Men shall then be equal to the angels.”
Source

Undated

date unknown
date
unknown
Glossa Ordinaria Medieval
“The measure of a man. According to the letter, holy John shows that the angel appeared to him in the form of a man, that he might openly denote that he who was signified was a true angel, that is, the Son of God, and was a true man.”
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.