The interpretation timeline
John 17:18 Douay-Rheims

As thou hast sent me into the world, I also have sent them into the world.

1270 – 1871 6 witnesses

Scholastic

c. 1100 – 1500
1270
A.D.
Thomas Aquinas Catholic
1225–1274
“Above, the Lord asked for the preservation of the disciples; here he asks for their sanctification. And first he asks for their sanctification; second, he assigns the necessity of the sanctification, at the place "as you sent me into the world"; third, he intimates the beginning of this sanctification, at the place "and for them I sanctify myself." He says therefore: I have asked in this way that they be kept from evil, but this is not sufficient unless they are perfected in good; Psalm 36:27: "Turn away from evil, and do good." And therefore, "Father, sanctify" — that is, perfect — "them," and make them holy. "And this in truth," that is, in me your Son, who am the truth, above, John 14:6, as if he were saying: make them partakers of my perfection and holiness. And therefore he adds "your word" — that is, your Word — "is truth," so that the sense is: sanctify them in me, the truth, because I, your Word, am the truth. Or, sanctify them by sending into them the Holy Spirit; and this in truth, that is, in the knowledge of the truth of faith and of your commandments; above, John 8:32: "You shall know the truth, and the truth shall set you free." For through faith and the knowledge of the truth we are sanctified; Romans 3:22: "For the justice of God is through faith in Jesus Christ, unto all and upon all who believe in him." And therefore he adds "your word is truth": because, namely, the truth of the words of God has no falsity mixed in with it; Proverbs 8:8: "My words are right, there is in them nothing crooked nor perverse." And because his word teaches uncreated truth. Or otherwise. In the Old Testament there was a manner of speaking, that everything which is set apart for divine worship is said to be sanctified; Exodus 28:1: "Bring to me Aaron your brother, with his sons, from among the children of Israel, that they may perform the office of priesthood for me." He says therefore "sanctify" — that is, set apart, as it were by way of sanctification — "them in the truth," that is, for the preaching of your truth: because "your word," which they must preach, "is truth." And the necessity of sanctification is subjoined when he says "as you sent me into the world, so I also have sent them into the world"; as if he were saying: I came for this, that I might preach the truth — below, John 18:37: "For this was I born... that I should give testimony to the truth"; so also I have sent the disciples to preach the truth; Mark, last chapter, 15: "Going into the whole world, preach the Gospel to every creature." They must therefore bear witness in truth; below, John 20:21: "As the Father has sent me, I also send you." But they must be sanctified not only on account of the office to which they are appointed, but because it has already been begun by me; hence he says "and for them I sanctify myself." For according to Augustine it must be known that in Christ there is a twofold nature: but as regards the divine, Christ is holy by essence, whereas as regards the human, Christ is holy by grace, which is derived from the divine nature. He says therefore, according to the divinity, "I sanctify myself," by assuming flesh for them: and this, so that the holiness of grace, which is from me as God in me as man, might be derived from me to them; because "of his fullness we have all received"; above, John 1:16. Psalm 132:2: "Like the ointment which is on the head" — of Christ, which is God — "which ran down upon the beard of Aaron" — that is, upon his humanity — and from this, "ran down upon the skirt of his garment" — that is, upon us. Or otherwise, according to Chrysostom, he asked that they be sanctified with a spiritual sanctification. But in the Old Testament there were carnal justifications; Hebrews 9:10: "justices of the flesh laid on them until the time of correction." But those were figures of spiritual sanctification, which nevertheless were brought about through some sacrifice; and therefore, for the sanctification of the disciples, it was fitting that some sacrifice be made. And this is what he says: that they themselves may be sanctified, I now sanctify myself — that is, I offer myself as a sacrifice; Hebrews 9:14: "he offered himself to God"; ibid. 13:12: "For which cause Jesus, that he might sanctify the people by his own blood, suffered outside the gate." And this in truth, not in figure, as in the Old Testament.”
Source

Post-Reformation

c. 1650 – 1900
1771
A.D.
John Gill Reformed
1697–1771
“And for their sakes I sanctify myself,.... Which is to be understood, not of his making himself holy; for he never was a sinner, and so stood in no need of sanctification: he was made like unto us, yet without sin; he looked like a sinner, but was not one; he was traduced, charged, and treated as such, but was perfectly holy, and free from all sin; he was essentially and infinitely holy as God; and as man, he was holy in his conception and birth; he was filled with the Holy Ghost, and was holy in his life and in his death: rather this may be meant of his being separated, and set apart for his office as Mediator, which, though done by the Father, and is ascribed unto him, Joh 10:36; yet may also be attributed to himself; since he voluntarily devoted himself to this work, and cheerfully accepted of it: though it seems best to understand it of his offering himself a sacrifice for, and in the room and stead of his people, in allusion to the offerings under the law, the sacrificing of which is expressed by sanctifying, Exo 13:2; and because his sacrifice was an Holy One: what he sanctified or offered was "himself": not his divine, but human nature, his body and his soul; and these as in union with his divine person; which gives his sacrifice the preference to all others, and is the true reason of its virtue and efficacy; and this is expressive of his great love. He himself is also the sanctifier or offerer, which shows him to be a priest, and that he had a power over his own life, and that he sacrificed it voluntarily; and this he is said to do at that present time, because the time was very near that he was to be offered up, and his present prayer and intercession were a part of his priestly office. This he did not for his own sake, nor for the sake of angels, nor for all men, but for his disciples, as distinct from the world; and not for the apostles only, but for all that the Father had given to him; and that as their substitute and surety, in their room and stead: that they also might be sanctified through the truth; that is, have all their sins expiated, and they be cleansed from all the guilt and filth of them, through Christ himself and his sacrifice, who is the truth; or "in truth"; as it may be rendered, really and truly, in opposition to the legal sacrifices which atoned for sin, not really, only typically; or through the. Gospel of truth, bringing the good news of atonement by the blood and sacrifice of Christ, and which the Spirit of God seals to the conscience with comfort and joy.”
Source
1832
A.D.
Adam Clarke Methodist
1762–1832
“As thou hast sent me - so have I also sent them - The apostles had the same commission which Christ had, considered as man - they were endued with the same Spirit, so that they could not err, and their word was accompanied with the same success.”
1849
A.D.
1774–1849
“As thou hast sent me into the world, I also have sent them into the world. He speaks of that mission, which agreed with him, as man, and become man for the salvation of mankind, to which also the apostles, and their successors were to co-operate, as the ministers and instruments of Christ, by virtue of their mission from him. (Witham) — For the same intent as Christ himself was sent, were the apostles sent also: whence St. Paul says, God was in Christ reconciling the world to himself, and he has placed in us the word of reconciliation. (2 Corinthians v. 19.) (Glossarium.)”
Source
1871
A.D.
1871
“As thou hast sent--sentest. me into the world, even so have I also sent them--sent I also them. into the world--As their mission was to carry into effect the purposes of their Master's mission, so our Lord speaks of the authority in both cases as co-ordinate.”

Undated

date unknown
date
unknown
Glossa Ordinaria Medieval
“As Thou hast sent Me into the world, even so have I also sent them into the world. For what Christ was sent into the world, for the same end were they; as saith Paul, God was in Christ reconciling the world unto Himself; and hath given to us the word of reconciliation. (2 cor. 5:19) As does not express perfect likeness between our Lord and His Apostles, but only as much as was possible in men. Have sent them, He says, according to His custom of putting the past for the future.”
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.