“And for their sakes I sanctify myself, that they also might be sanctified through the truth.”
John 17:19 — Greek Interlinear
Church Fathers on John 17:19
Again, our Lord gives a reason why the disciples are worthy your of obtaining such favor our from the Father: I have given them your word; and the world has hated them; i.e. They are had in hatred for your sake, and on account of your word.
They had not yet experienced these sufferings which they afterwards met with; but, after His custom, He puts the future into the past tense. Then He gives the reason why the world hated them; viz. Because they are not of the world. This was conferred upon them by regeneration; for by nature they were of the world. It was given to them that they should not be of the world, even as He was not of the world; as it follows; Even as I am not of the world. He never was of the world;…
As if to say, The time is now at hand, when I shall be taken out of the world; and therefore it is necessary that they should be still left in the world, in order to preach Me and You to the world. But that you should keep them from the evil; every evil, but especially the evil of schism.