Albert Barnes Commentary John 17:20-21

"Neither for these only do I pray, but for them also that believe on me through their word; that they may all be one; even as thou, Father, [art] in me, and I in thee, that they also may be in us: that the world may believe that thou didst send me." — John 17:20-21 (ASV)

Neither pray I for these alone, and so on. This prayer is not for the apostles only, but for all who will be converted under the preaching of the gospel. They will all need similar grace and be exposed to similar trials.

It is a matter of unspeakable joy that each Christian—however humble or unknown to men, however poor, unlearned, or despised—can reflect that he was remembered in prayer by him whom God heareth always. We value the prayers of pious friends. How much more should we value this petition of the Son of God!

To that single prayer, we who are Christians owe infinitely more real benefits than the world can ever bestow. In the midst of any trials, we may remember that the Son of God prayed for us, and that the prayer was assuredly heard and will be answered for all who truly believe.

All may be one. This means they may be united as fellow believers. Christians are all redeemed by the same blood and are going to the same heaven. They have the same needs, the same enemies, and the same joys.

Though they are divided into different denominations, they will meet at last in the same abodes of glory. Therefore, they should feel that they belong to the same family and are children of the same God and Father.

There are no ties so tender as those which bind us in the gospel. There is no friendship so pure and enduring as that which results from having the same attachment to the Lord Jesus. Therefore, Christians in the New Testament are represented as being indissolubly united—parts of the same body and members of the same family (Acts 4:32–35; 1 Corinthians 12:4–31; Ephesians 2:20–22; Romans 12:5).

On the ground of this union, they are exhorted to love one another, to bear one another's burdens, and to pursue the things that make for peace and things with which one may edify another (Ephesians 4:3; Romans 12:5–16).

As thou, Father, art in me . This does not affirm that the union between Christians should be in all respects like that between the Father and the Son, but only in the points in which they are capable of being compared. It is not the union of nature that is referred to, but the union of plan, of counsel, of purpose—seeking the same objects, manifesting attachment to the same things, and a desire to promote the same ends.

That they also may be one in us. To be in God and in Christ is to be united to God and Christ. The expression is common in the New Testament. The phrase used here denotes a union among all Christians founded on and resulting from a union to the same God and Saviour.

That the world may believe, and so on. That the world, so full of animosities and conflicts, may see the power of Christian principle in overcoming the sources of contention and producing love, and may thus see that a religion that could produce this must be from heaven (see Barnes on John 13:34).

This was done. Such was the attachment of the early Christians to each other that a non-Christian was compelled to say, "See how these Christians love one another!"