Thomas Aquinas

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.