Augustine of Hippo
Catena Aurea · Johannesevangelium 17
I have given them thy word; and the world hath hated them, because they are not of the world, even as I am not of the world. I pray not that thou shouldest take them out of the world, but that thou shouldest keep them from the evil. They are not of the world, even as I am not of the world. Sanctify them through thy truth; thy word is truth. As thou hast sent me into the world, even so have I also sent them into the world. And for their sakes I sanctify myself, that they also might be sanctified through the truth.
(Tr. cviii) Sanctify them through Thy truth: for thus were they to be kept from the evil. But it may be asked, how it was that they were not of the world, when they were not yet sanctified in the truth? Because the sanctified have still to grow in sanctity, and this by the help of God’s grace. The heirs of the New Testament are sanctified in that truth, the shadows of which were the sanctification of the Old Testament; they are sanctified in Christ, Who said above, I am the way, the truth, and the life. (c. 14:6) It follows, Thy discourse is truth. The Greek is λόγος, i. e. word. The Father then sanctified them in the truth, i. e. in His Word the Only-Begotten, them, i. e. the heirs of God, and joint-heirs with Christ.