Today's section of the Gospel starts with the important lesson that we are to be in the world but not of it: though our tasks is to transform the world, to convert it to Christ to there is nothing at all wrong with building up the walls of the Church to keep evil out! The second part of the chapter widens Christ's prayer to all believers down the ages.
The New Advent page has the Greek, Latin and Knox translation. You can listen to the Latin here and the Greek here.
14 Ego dedi eis sermonem tuum, et mundus eos odio habuit, quia non sunt de mundo, sicut et ego non sum de mundo. 15 Non rogo ut tollas eos de mundo, sed ut serves eos a malo. 16 De mundo non sunt, sicut et ego non sum de mundo. 17 Sanctifica eos in veritate. Sermo tuus veritas est. 18 Sicut tu me misisti in mundum, et ego misi eos in mundum: 19 et pro eis ego sanctifico meipsum: ut sint et ipsi sanctificati in veritate.20 Non pro eis autem rogo tantum, sed et pro eis qui credituri sunt per verbum eorum in me: 21 ut omnes unum sint, sicut tu Pater in me, et ego in te, ut et ipsi in nobis unum sint: ut credat mundus, quia tu me misisti. 22 Et ego claritatem, quam dedisti mihi, dedi eis: ut sint unum, sicut et nos unum sumus. 23 Ego in eis, et tu in me: ut sint consummati in unum: et cognoscat mundus quia tu me misisti, et dilexisti eos, sicut et me dilexisti. 24 Pater, quos dedisti mihi, volo ut ubi sum ego, et illi sint mecum: ut videant claritatem meam, quam dedisti mihi: quia dilexisti me ante constitutionem mundi. 25 Pater juste, mundus te non cognovit, ego autem te cognovi: et hi cognoverunt, quia tu me misisti. 26 Et notum feci eis nomen tuum, et notum faciam: ut dilectio, qua dilexisti me, in ipsis sit, et ego in ipsis.
 I have given them thy word, and the world hath hated them, because they are not of the world; as I also am not of the world.  I pray not that thou shouldst take them out of the world, but that thou shouldst keep them from evil.  They are not of the world, as I also am not of the world.  Sanctify them in truth. Thy word is truth.  As thou hast sent me into the world, I also have sent them into the world.  And for them do I sanctify myself, that they also may be sanctified in truth.  And not for them only do I pray, but for them also who through their word shall believe in me;
 That they all may be one, as thou, Father, in me, and I in thee; that they also may be one in us; that the world may believe that thou hast sent me.  And the glory which thou hast given me, I have given to them; that they may be one, as we also are one:  I in them, and thou in me; that they may be made perfect in one: and the world may know that thou hast sent me, and hast loved them, as thou hast also loved me.  Father, I will that where I am, they also whom thou hast given me may be with me; that they may see my glory which thou hast given me, because thou hast loved me before the creation of the world.  Just Father, the world hath not known thee; but I have known thee: and these have known that thou hast sent me.  And I have made known thy name to them, and will make it known; that the love wherewith thou hast loved me, may be in them, and I in them.
Catena Aurea page on being in the world not of it:
BEDE. 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.
AUG. He repeats the same thing again; They are not of the world, even as I am not of the world.
CHRYS. Above, when He said, Then whom you gave Me out of the world, He meant their nature; here He means their actions. They are not of the world; because they have nothing, in common with earth they are made citizens of heaven. Wherein He shows His love for them, thus praising them to the Father. The word as when used with respect to Him and the Father expresses likeness of nature; but between us and Christ there is immense distance Keep them from the evil, i.e. not from dangers only, but from falling away from the faith.
Prayer for all believers:
AUG. When our Lord had prayed for His disciples, whom He named also Apostles, He added a prayer for all others who should believe on Him; Neither pray I for these alone, but for all others who shall believe of Me through their word.
CHRYS. Another ground of consolation to them, that they were to be the cause of the salvation of others.
AUG. All, i.e. not only those who were then alive, but those who were to be born; not those only who heard the Apostles themselves, but us who were born long after their death. We have all believed in Christ through their word: for they first heard that word from Christ, and then preached it to others, and so it has come down, and will go down to all posterity. We may see that in this prayer there are some disciples whom He does not pray for; for those,
i.e. who were neither with Him at the time, nor were about to believe on Him afterwards through the Apostles' word, but believed already.
Was Nathanael with Him then, or Joseph of Arimathea, and many others, who, John says, believed on Him? I do not mention old Simon, or Anna the prophetess, Zacharias, Elisabeth, or John the Baptist; for it might be answered that it was not necessary to pray for dead persons, such as these who departed with such rich merits. With respect to the former then we must understand that they did not yet believe in Him, as He wished, but that after His resurrection, when the Apostles were taught and strengthened by the Holy Spirit, they attained to a right faith.
The case of Paul however still remains, An Apostle not of men, or by men; and that of the robber, who believed when even the teachers themselves of the faith fell away. We must understand then, their word, to mean the word of faith itself which they preached to the world; it being called their word, because it was preached in the first instance and principally by them; for it was being preached by them, when Paul received it by revelation from Jesus Christ Himself. And in this sense the robber too believed their word. Wherefore in this prayer the Redeemer prays for all whom He redeemed, both present and to come.
The call to unity in Christ, true ecumenism through the reconciliation of all believers to the Catholic Church:
HILARY. And this unity is recommended by the great example of unity: As you, Father, are in Me, and I in you, that they also may be one in Us, i.e. that as the Father is in the Son, and the Son in the Father, so after the likeness of this unity, all may be one in the Father and in the Son.
CHRYS. For there is no scandal so great as division, whereas unity amongst believers is a great argument for believing; as He said at the beginning of His discourse, By this shall all men know that you are My disciples, if you have love one to another. For if they quarrel, they will not be looked on as the disciples of a peacemaking Master. And I, He says, not being a peacemaker, they will not acknowledge Me as sent from God.