John 17:19

And for their sakes I sanctify Myself, that they also might be sanctified through the truth.

Only one means Jesus knows of, both for working faith and for keeping in the faith, and that means He has given to the disciples: the Word of the Father. There is no need of following the lead of enthusiasts that prate of new revelations, the inner light, and keys to the Scriptures. The Word of the Gospel as we have it in Scriptures is all-sufficient for all needs. But the Word thus becomes a distinguishing factor, since the Christians accept it, and the world, the unbelievers, refuses to recognize its worth and power. The result is that the unbelieving world hates the Christians. Their acceptance of the Gospel is a constant accusation of the world's rejection of Christ; it emphasizes the essential difference between believers and unbelievers. The former have nothing in common with the world, with the nature and manner of the children of the world. The attitude toward the Word of the Gospel is the deciding factor; the Word is the touchstone by which men decide their fate. The Word therefore is the rock-foundation of a Christian's faith. "There I have the Word of Christ, my Lord, yea, of the almighty Father in heaven; that I know and am certain, if I cling to that, then no power on earth nor the gates of hell can harm me, for He loves His Word and will hold His hand over it, and therefore also protect and defend all that cling to it. " The Christians, then, are perfectly willing and satisfied to occupy the position in which the world places them by its hatred, since thereby they are identified more fully with Christ. Purposely, therefore, Jesus does not ask that the believers be taken out of the world, that they be removed from the proximity of harm and danger and hatred, but only that the Father would keep them, shield them against the wiles of the devil. That is the one side of the Christians' preservation in faith, which is the work of God. God guards and protects them from their enemies, the world and the devil, by not permitting these enemies to seduce them, nor lead them into misbelief, despair, or other great shame and vice. That danger is always present, and many a believer has been overcome, since he did not trust in the power of God alone. What Jesus here prays should be remembered by all Christians at all times: They do not belong to the world, as I am not of the world. Christ and the unbelieving world have nothing in common; and so the followers of Christ and the unbelieving world can have nothing in common. Their interests, their objects, lie in opposite directions and can never be reconciled. To attempt a compromise with the unbelieving world is to make peace with the devil. And therefore the prayer of Jesus takes this factor into account. He asks that God complete the separation between the believers and the world, sanctify the disciples wholly by consecrating them to God alone, through the power of the Word. The Christians are sanctified, separated from the world, as soon as faith has been wrought in their hearts. But it is the power of God in the Word which must continue to keep them separated and consecrated. And this sanctification and these fruits of faith are not our work and ability, but God's mercy and divine power. The believers being thus set apart through the power of the Word, they are ready for their great ministry. Even as God sent the Son into the world to preach and bring salvation, so the Son, in turn, sends the believers out into the world to preach the redemption that has been earned by Jesus. They should be witnesses for the truth, they should confess Christ. They are His witnesses to the world, for all men are included both under sin and under grace, John 3:16. In the midst of the unbelieving world Christ wanted to build His Church. And in order that this might be accomplished, in order that the work of the disciples might be done with the feeling of free and full consecration, Jesus consecrates Himself, gives Himself as a sacrifice for the whole world. He is about to enter upon His Passion now to work a perfect redemption. And every believer that accepts this deliverance, this redemption, thereby is separated from the hostile, unbelieving world and consecrated in and for the truth of the Gospel. Thus the disciples are sanctified and remain sanctified; they remain in the Word of Truth, in and through which the sin which persists in troubling them is forgiven, and they receive strength both to combat the evil and to carry out the will of the Lord for the proclamation of the Word to others.