Keeping the believers in God's name: V. 12. While I was with them in the world, I kept them in Thy name; those that Thou gavest Me I have kept, and none of them is lost but the son of perdition, that the Scripture might be fulfilled. V. 13. And now I come to Thee; and these things I speak in the world, that they might have My joy fulfilled in themselves.
As long as Jesus was present in the world, in the flesh, so long He personally tended to the keeping of His disciples in the faith. He taught, He admonished them day by day; He always revealed anew to them the name of the Father, in the Gospel which He proclaimed. And His Gospel-work had been most successful. He had kept all of the disciples whom the Father had given Him, His watchful guiding and warning had not been in vain but only in one single case, that of the son of perdition, of the traitor. In his case the Scripture had to be fulfilled. Cp. Ps. 69, 4; Acts 1, 20.
But now the sojourn of Christ on earth was drawing to a close; no more would He be present with His disciples in the terms of personal, visible contact to which they had become accustomed. Jesus was going to the Father, and therefore He was making this prayer in their presence, while He was yet in the world, that they might be convinced of His personal interest in them, of His unchanging solicitude for them. His urgent prayer for their preservation in the faith should give them the assurance, as it should to the believers of all times, that nothing is left undone which will assist them in the midst of all the perils of the world and their own flesh.
That is a source of wonderful comfort to the believers, that gives them the fullness of joy. Theirs, then, is a joy in Christ; they are happy over the fact that they are Christians, that they are intimates of the Father. This joy must drive out every bit of doubt as to a person's remaining in faith to the end, just as this entire section of Christ's prayer contains nothing but comfort for every Christian. Where there is such intimacy as between God and Christ, on the one hand, and the believers, on the other, all fear and doubts must vanish.
"Now if some one wants to know whether he is elected or in what relation he stands to God, let him but look upon the mouth of Jesus, that is, upon these and similar verses. For though a person cannot say of a certainty who will be elected in the future and remain to the end, yet this is certainly true, that whosoever is called and comes there, namely, to hear this revelation, that is, the Word of Christ, provided he accept it in all sincerity, that is, fully hold and believe that it is true, they are the ones that are given to Christ by the Father . But those that are given to Him He will surely keep, and insist that they do not perish" (Luther, 8, 779).