The interpretation timeline
John 18:21 Douay-Rheims

Why asketh thou me? ask them who have heard what I have spoken unto them: behold they know what things I have said.

A.D. 407 – 1871 5 witnesses

Patristic

before A.D. 750
407
A.D.
John Chrysostom Patristic
A.D. 347–407
“(Hom. lxxxiii) Or, He spoke in secret, but not, as these thought, from fear, or to excite sedition; but only when what He said was above the understanding of the many. To establish the matter, however, upon superabundant evidence, He adds, Why askest thou Me? ask them which heard Me what I said unto them; behold, they know what I said unto them: as if He said, Thou askest Me of My disciples; ask My enemies, who lie in wait for Me. These are the words of one who was confident of the truth of what He said: for it is incontrovertible evidence, when enemies are called in as witnesses.”
Source

Scholastic

c. 1100 – 1500
1270
A.D.
Thomas Aquinas Catholic
1225–1274
“Here it is set forth how the Lord, having been seized by the officers, is presented to the chief priests: first, how he is led to one chief priest, namely Annas; second, how he is led to the other, namely Caiaphas, at the place "and Annas sent him bound to Caiaphas." Concerning the first he does two things. First he tells how he is presented to Annas; second, how he is examined by Annas, at the place "the high priest therefore questioned Jesus." Concerning the first he does two things. First he sets forth how he is led to the house of Annas; second, how the disciples follow him, at the place "and Simon Peter followed Jesus, and another disciple." Concerning the first, first it is shown what was done regarding Jesus; second, the high priest himself, to whom he is led, is described, at the place "now he was the father-in-law of Caiaphas." Now concerning Christ three things were done. For first he is seized; hence he says, "the cohort therefore" — that is, of soldiers — "and their tribune, and the officers of the Jews, seized Jesus," who is incomprehensible; Jeremiah 32:19: "great in counsel, and incomprehensible in thought." For perhaps they were thinking of that saying, Psalm 70:11: "God has forsaken him: pursue and seize him, for there is none to deliver him"; Lamentations 4:20: "the breath of our mouth, Christ the Lord, was taken in our sins," that is, on account of our sins, namely that he might set us free; Isaiah 49:25: "indeed, the captivity shall be taken away from the strong." Second, he is bound; hence he says, "and they bound him" — he who came to loose the bound and to burst their bonds; Psalm 115:17: "you have burst my bonds," and so on. Third, he is led away; hence he says, "and they led him to Annas," that they might destroy him who came to lead all men into the way of salvation; Psalm 60:4: "you have led me, because you have become my hope." A twofold reason can be assigned why he was led to Annas first. One is the command of Caiaphas, the high priest of that year, who sent Jesus to Annas for this reason: that he might be the more excusable if he himself afterward condemned one already condemned by Annas. The other reason is the nearness of the house of Annas, which, being situated along the way, was closer. And so, fearing lest, if a tumult of the people should be stirred up, Jesus be snatched from their hands, they turned aside there. Here first the high priest is described from his relation to Caiaphas, because he was his father-in-law; second, Caiaphas himself is described, because he was the high priest of that year. For it must be known that, according to the law, the high priest held the office for his whole life, and after his death his son succeeded him. But afterward, as the envy and ambition of the leading men grew, not only did the son not succeed the father, but no one held the office of the high-priesthood beyond a year, and this very thing was procured by money, as Josephus says. And therefore it is no wonder if, in the year of a high-priesthood acquired so wickedly, he carried out so heinous a deed. He is also described by his counsel; hence he said, "now Caiaphas was he who had given counsel to the Jews" — above, John 11:50 — namely this, that it is expedient that one man die for the people. The Evangelist recalled this in order to remove scandal from the hearts of the faithful, showing, even through the prophecies of his adversaries, that he was not seized and put to death on account of his own weakness or powerlessness, but for the salvation of the people, namely that the whole nation should not perish. For the testimony of an adversary is more effective; and truth is of such a nature that even an adversary cannot keep silent about it. Here it is set forth how the disciples accompanied Christ: first it is set forth how Peter, with another disciple, followed Christ; second, how they entered into the place where Christ was; third, how he denied him. He says, then, as to the first, "now Simon Peter followed Jesus" — out of devotion, although from afar on account of fear — "and another disciple," namely John, whose name he himself conceals for humility's sake. And by this it is given to be understood that the rest of the disciples had fled, having abandoned Jesus, as is said in Matthew 26:56. Mystically, however, by these two disciples two lives are understood, which follow Christ: namely, the active life, which is signified by Peter, and the contemplative life, which is signified by John. And the active life indeed follows Christ by obeying — above, John 10:27: "my sheep hear my voice" — the contemplative, however, by knowing and contemplating, Hosea 6:3: "we shall know, and we shall follow you." Now these two disciples followed because they loved Christ more than the rest — hence they were the first to come to the tomb, below, John 20:2 — and because a greater force of love united them to one another; hence they are often joined together in the Gospel; and in the Acts of the Apostles it is said that they sent to them Peter and John. And again: Peter and John went up into the temple at the ninth hour of prayer. Here it is set forth how Peter entered, as to the order: first, how John went in before him; second, how he brought Peter in, at the place "the other disciple therefore went out," and so on. Now the order was this: that John entered first with Jesus. And the reason for this was that he was known to the high priest, while Peter stood at the door of the court outside. And although John had been a fisherman, and a young man called by Christ, he was nevertheless known to the high priest — either because John's father was a servant to him, or because some one of his kinsmen was. Nor did John set this down out of boastfulness of himself, but out of humility, lest the fact that he entered before Peter with Jesus into the court of the high priest, and not Peter, be ascribed rather to his own virtue and higher standing than to acquaintance. And therefore he says, "that disciple" — namely John — "was known to the high priest": and therefore he entered with Jesus into the court of the high priest, where Christ had been led. But Peter stood outside — as it were presaging his future denial; Psalm 30:13: "they who saw me fled outside from me." Mystically, however, John enters with Jesus, because the contemplative life is familiar to him; Wisdom 8:16: "entering into my house, I shall repose with her." But Peter stands outside, because the active life is occupied with exterior things; Luke 10:39: "Mary, sitting beside the Lord's feet, was listening to his word. But Martha was busied about much serving." Here it is shown how Peter was brought in through John's intervention: because that other disciple, namely John, was known to the high priest, and spoke to the doorkeeper, that she might bring him in, and brought Peter in. By which it is mystically given to be understood that the active life is brought in to Christ through the contemplative: for just as the lower reason is directed by the higher, so the active life is directed through the contemplative; Psalm 42:3: "send forth your light and your truth: they have led me and brought me unto your holy mountain, and into your tabernacles." Here Peter's denial is set forth: first the motive of the denial, or the occasion, is set forth; second the denial itself is set forth, at the place "he says: I am not"; third the confirmation of the denial, at the place "now the servants and officers stood at the coals." Now the occasion and motive of the denial for Peter was the maidservant's question; hence he says, "the maidservant, the doorkeeper, said to Peter: are you not also one of his disciples?" Now she says "you also," because she knew John to be a disciple of Christ, and yet, on account of familiarity, says nothing to him. Now Peter's weakness for that time appears in this, that he was moved to deny from a feeble occasion; and this on two counts. First, from the very person questioning: for it was not an armed soldier, not an awe-inspiring high priest, but a woman, a maidservant and doorkeeper, who questioned him. Second, from the form of the question: for she does not say, "are you not one of the disciples of this traitor?" By which she seemed rather to speak out of compassion. Hence, from this too, it is perceived that "by the word of the Lord the heavens were established, and all their power by the breath of his mouth," Psalm 32:6 — because he who denied Christ at the voice of a maidservant afterward confesses and preaches the name of Christ before the chief priests; Acts 4:8 and following. Peter's denial is set forth when he says, "he says: I am not." In which we ought to note, according to Augustine, that Christ is denied not only by him who says that he is the Christ, but also by him who denies that he himself is a Christian. Now Peter, in this manner, denied nothing else than that he was a Christian. Now the Lord permitted Peter to deny him for this reason: because he willed that he himself, who was to be set over the whole Church, should have greater compassion on the weak and on those who sin, having experienced in himself the weakness of sin; Hebrews 4:15: "we do not have a high priest who cannot have compassion on our infirmities, tempted in all things, yet without sin" — this is true of Christ, but of Peter it can be said even with sin. Some, however, attributing a certain vain grace to Peter, say that he denied not out of fear, but out of love, wishing always to be with Christ and to follow continually; for he knew that if he confessed himself to be one of Christ's disciples, he would have been separated from Christ and driven away. But this does not agree with the Lord's own words: for he did not deny for the reason that he did not wish to be separated from Christ, but because he did not wish to lay down his life for Christ. For above, when he had said, "I will lay down my life for you," Jesus answered: "will you lay down your life for me? Amen, amen I say to you: the cock shall not crow before you deny me three times." The confirmation of the denial is set forth at the place "now the servants and the officers stood at the coals... and Peter also was with them" — as it were, so that he might seem all the more not to be his disciple. For Peter, so that he might not seem to be one of the disciples, placed himself among the officers and servants standing at the coals, because it was cold — as sometimes happens at the winter equinox in March; in which Peter did not well consider what is said in Psalm 17:26: "with the holy you shall be holy... and with the perverse you shall be perverted." Even the season itself agrees with the condition of his mind, in which charity had grown cold; Matthew 24:12: "the charity of many shall grow cold, because iniquity has abounded." "The high priest therefore questioned Jesus" — where first the examination is set forth; second, Christ's response, at the place "Jesus answered him"; third, the reproof of the response, at the place "now when he had said these things," and so on. Now two things were imputed to Christ by the Jews: namely, false doctrine, and new doctrine; Mark 1:27: "what is this new doctrine?" Second, sedition, and the drawing of men to himself; Luke 23:5: "he has stirred up the people throughout all Judea, beginning from Galilee even to this place." And therefore he examines him concerning these two things: first indeed concerning his disciples, whom he saw he had seduced; second concerning his doctrine, as it were marking it with falsity. Here the Lord's response is set forth: first he sets forth the manner of his doctrine; second he requires the testimony of others, at the place "why do you question me?" Concerning the first he does two things: first he proposes the manifestness of his doctrine; second he explains it. He says therefore: "I have spoken openly to the world." But against this: above, John 16:25, he says: "the hour comes when I will announce to you concerning the Father, not in proverbs, but openly." If then he had not yet spoken openly to the disciples, how did he speak openly to the world? Response: it must be said that he was not yet speaking openly to the disciples, because he was proposing surpassing teachings; but he spoke openly to the world, because he was preaching publicly. Hence he explains this, saying: "I have always taught in the temple and in the synagogues." But against this: it is said in Matthew 16 that he proposed many things to the disciples apart, without parables. But to this there is a threefold response. One, that what he was saying to the twelve disciples was not reckoned as being said in secret. The other is that he did not propose these things to the disciples with the intention of concealing them. Third, if weight is placed on the word, because the Lord here speaks of the doctrine which he handed down to the people, which he did not set forth to them in private gatherings, but in public places; Psalm 39:10: "I have announced your justice in the great church"; Isaiah 45:19: "I have not spoken in secret, in a place of the dark land." And to this he requires the testimony of others, saying: "why do you question me? Ask those who have heard what I have spoken to them": and first he refers them to the testimony of others; second he shows whose testimony he requires; third he assigns the reason for these. As to the first he says, "why do you question me?" — as if he were to say: through others you can know this. And therefore, as to the second, he adds, "ask those who have heard." For, as is said in Matthew 22:15, the Pharisees sent to Jesus, that they might catch him in speech; who nevertheless were able to find nothing against him. And therefore he refers him to them. And he adds the reason for this: "behold, these know what I have said" — of whom testimony can be given.”

Post-Reformation

c. 1650 – 1900
1771
A.D.
John Gill Reformed
1697–1771
“Why askest thou me?.... He seems surprised at the high priest's conduct, that he should put such questions to him, who stood bound before him; was brought there as a criminal, and was the defendant, and not obliged to accuse himself; nor could it be thought, that whatever evidence or testimony he should give, would have much weight with the persons before whom he stood. Ask them which heard me, what I said unto them; he appeals to his hearers, many of whom were then present; and these his enemies, even his worst enemies, so clear was his case, so free was his doctrine from sedition and blasphemy, so innocent was he in the whole of his deportment and conduct, that he even submits to have his case issued and determined by what his hearers should say of him; and these not his friends, but his enemies; see Isa 50:8; behold, they, or these, know what I have said; pointing at some persons present, perhaps the very officers who had been sent to take him before, but returned without him, declaring that never man spake like him.”
Source
1849
A.D.
1774–1849
“Why askest thou me? Caiphas, in quality of judge, was to examine the crimes laid to the charge of the accused, by the testimony of the witnesses. (Witham)”
1871
A.D.
1871
“Why askest thou me? ask them which heard me . . . they know what I . . . said--This seems to imply that He saw the attempt to draw Him into self-crimination, and resented it by falling back upon the right of every accused party to have some charge laid against Him by competent witnesses. (Also see on Mar 14:54.)”
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.