The interpretation timeline
Luke 9:32 Douay-Rheims

But Peter and they that were with him were heavy with sleep. And waking, they saw his glory, and the two men that stood with him.

A.D. 253 – 1871 11 witnesses 19 excerpts

Patristic

before A.D. 750
253
A.D.
Origen Patristic
c. A.D. 184–253
“(ubi sup.) Now Jesus wishes not those things which relate to His glory to be spoken of before His passion. Hence it follows, And they kept it close. For men would have been offended, especially the multitude, if they saw Him crucified Who had been so glorified.”
379
A.D.
Basil of Caesarea Patristic
c. A.D. 330–379
“(in Esai. c. 4. 5.) For the obscurity of the Law had passed away; for as smoke is caused by the fire, so the cloud by light; but because a cloud is the sign of calmness, the rest of the future state is signified by the covering of a cloud.”
397
A.D.
Ambrose of Milan Patristic
A.D. 339–397
“For the incomprehensible brightness of the Divine nature oppresses our bodily senses. For if the sight of the body is unable to contain the sun’s ray when opposite to the eyes which behold it, how can the corruption of our fleshly members endure the glory of God? And perhaps they were oppressed with sleep, that after their rest they might behold the sight of the resurrection. Therefore when they were awake they saw His glory. For no one, except he is watching, sees the glory of Christ. Peter was delighted, and as the allurements of this world enticed him not, was carried away by the glory of the resurrection. Hence it follows, And it came to pass as they departed, &c.”
Source
“Nor does the condition of man in this corruptible body allow of making a tabernacle to God, whether in the soul or in the body, or in any other place; and although he knew not what he said, yet a service was offered which not by any deliberate forwardness, but its premature devotion, receives in abundance the fruits of piety. For his ignorance was part of his condition, his offer of devotion.”
Source
“For it is the overshadowing of the divine Spirit which does not darken, but reveals secret things to the hearts of men.”
“They then departed, when our Lord’s manifestation had begun. There are three seen at the beginning, one at the end; for faith being made perfect, they are one. Therefore are they also received into the body of Christ, because we also shall be one in Christ Jesus; or perhaps, because the Law and the Prophets came out from the Word.”
Source
407
A.D.
John Chrysostom Patristic
A.D. 347–407
“(Hom. 56. in Matt.) Or, by the word sleep, he means that strange maze that fell upon them by reason of the vision. For it was not night time, but the exceeding brightness of the light weighed down their weak eyes.”
444
A.D.
A.D. 376–444
“For perhaps holy Peter imagined that the kingdom of heaven was at hand, and therefore it seemed good to him to abide on the mount.”
“He knew not what he said, for neither was the time come for the end of the world, or for the Saints’ enjoyment of their promised hope. And when the dispensation was now commencing, how was it fitting that Christ should abandon His love of the world, Who was willing to suffer for it?”
735
A.D.
Bede the Venerable Patristic
c. A.D. 672–735
“And mark, that as when our Lord was baptized in Jordan, so also when He was glorified on the Mount, the mystery of the whole Trinity is declared; for His glory which we confess at baptism, we shall see at the resurrection. Nor in vain does the Holy Spirit appear here in the cloud, there in the form of a dove, seeing that he who now preserves with a simple heart the faith which he receives, shall then in the light of open vision look upon those things which he believed.”
Source
749
A.D.
John of Damascus Patristic
A.D. 676–749
“(Orat. de Trans. fig.) It were not good for thee, Peter, that Christ should abide there, for if He had remained, the promise made to thee would never receive its accomplishment. For neither wouldest thou have obtained the keys of the kingdom, nor the tyranny of death been abolished. Seek not bliss before its time, as Adam did to be made a God. The time shall come when thou shalt enjoy the sight without ceasing, and dwell together with Him who is light and life.”
Source
“(ubi sup.) It behoved Him also not to confine the fruit of His incarnation to the service of those only who were on the mount, but to extend it to all believers, which was to be accomplished by His cross and passion.”
“(ubi sup.) This also our Lord commands, since He knew His disciples to be imperfect, seeing that they had not yet received the full measure of the Spirit, lest the hearts of others who had not seen should be prostrated by sorrow, and lest the traitor should be stirred up to a frantic hatred.”

Scholastic

c. 1100 – 1500
1107
A.D.
c. 1055–1107
“While Christ is engaged in prayer, Peter is heavy with sleep, for he was weak, and did what was natural to man; as it is said, But Peter and they that were with him were heavy with sleep. But when they awake, they behold His glory, and the two men with Him; as it follows, And when they were awake, they saw his glory, and the two men, that stood with him.”
Source
“Lest in truth any one should suppose that these words, This is my beloved Son, were uttered about Moses or Elias.”
“Now those things which began from the Word, end in the Word. For by this he implies that up to a certain time the Law and the Prophets appear, as here Moses and Elias; but afterwards, at their departure, Jesus is alone. For now abideth the Gospel, legal things having passed away.”

Reformation

c. 1500 – 1650
1637
A.D.
1567–1637
“But Peter and they that were with Him were heavy with sleep. S. Chrysostom takes sleep to mean amazement. But we may rather accept the words simply as describing the natural sleep which had fallen on the Apostles after the fatigue of their journey and watchings, from which they were awakened by the brightness of the transfiguration. See S. Matt. xvii. 1”
Source

Post-Reformation

c. 1650 – 1900
1771
A.D.
John Gill Reformed
1697–1771
“While he thus spake there came a cloud,.... While Peter was making the above request, before an answer was returned, a cloud appeared, a very uncommon one, as a symbol of the divine presence: "and overshadowed them"; Jesus, Moses, Elias, and the disciples: and they feared as they entered into the cloud; either as they themselves entered into it, that coming gradually over them, because of the glory of it, and the solemnity that attended it; or as Moses and Elias entered into it; and so the Syriac and Persic versions read, "they feared when they saw Moses and Elias enter into the cloud"; which took them out of their sight: just as the cloud received Jesus out of the sight of his disciples, when he ascended to heaven, Act 1:9.”
Source
1871
A.D.
1871
“and when they were awake--so, certainly, the most commentators: but if we translate literally, it should be "but having kept awake" [MEYER, ALFORD]. Perhaps "having roused themselves up" [OLSHAUSEN] may come near enough to the literal sense; but from the word used we can gather no more than that they shook off their drowsiness. It was night, and the Lord seems to have spent the whole night on the mountain (Luk 9:37). saw his glory, &c.--The emphasis lies on "saw," qualifying them to become "eye-witnesses of His majesty" (Pe2 1:16).”
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.