John 17:21

Jesus prayed for the unity of all believers as well as for the unity of the Eleven (John 17:11). This unity rests on adherence to God’s truth, and it reflects the unity that exists between the Father and the Son. Furthermore it is union with the Father and the Son (cf. ch. 15). God answered this prayer initially on the day of Pentecost when He united believers with Himself in the body of Christ, the church (cf. 1 Corinthians 12:13).

The purpose of this unity is that the world might believe that the Father sent the Son, namely, that Jesus was God’s Son. The display of mutual love among Jesus’ disciples shows that they are His disciples. Their love for one another shows that they really do follow His teachings and possess His life. This gives evidence that Jesus really was who He claimed to be. It vindicates His teaching and so glorifies Him.

"From the beginning of the believer’s spiritual life to his final glorification the fatherhood of God is the basis for the believer’s experience. . . . This relationship of God to men, perfectly exemplified in the life of the Lord Jesus Christ, is both the highest expression of His consciousness of His relation to God and the fullest attainment that man can reach through union with Him." [Note: Tenney, "Topics from . . .," p. 46.]

This verse is a favorite of promoters of the ecumenical movement. However as the content and context of this verse clarify, Jesus was not speaking about institutional unity but personal unity among genuine believers. He was praying that all true believers would be one in their love for one another, their submission to the authority of Scripture, and their commitment to their mission. Disunity among professing Christians has frustrated Jesus’ purpose that the world might believe on Him. Nevertheless the solution to this problem is not to impose an artificial institutional unity that ignores the bases of true unity and presents a hypocritical facade of oneness. It is to promote love for one another among genuine believers.