John 17:21

For those who through their preaching believe on Him He prays that they may be one. Naturally the extension of the Church imperils its unity, the ἑνότης τοῦ πνεύματος, Ephesians 4:3. “This unity is infinitely more than mere unanimity, since it rests upon unity of spirit and life.” Tholuck. This unity of all believers finds its ideal in the unity of the Father and the Son: καθὼς σὺ, πάτερ κ. τ. λ., and not only its ideal but its unifying principle and element, ἐν ἡμῖν. This unity of all believers is to result in the universal belief in Christ's mission, ἵνα ὁ κόσμος … ἀπέστειλας.