Be one in Jesus

John 17:20-26

In ourselves we cannot be one, severed from each other by diverse pleasures, and lusts, and the pollution of sin, from which we must be cleansed by a Mediator, in order to be one in Him. For there is no scandal so great as division, whereas unity amongst believers is a great argument for believing; as Jesus said at the beginning of His discourse, "By this shall all men know that you are My disciples, if you have love one to another". For if they quarrel, they will not be looked on as the disciples of a peacemaking Master. And they will not acknowledge Jesus as sent from God.

Jesus said: "Righteous Father, the world also does not know you" as if He were troubled at the thought that they should be unwilling to know One so just and good. While the Jews had said, that they knew God, and that Jesus did not, Jesus on the contrary said: "but I know You, and they know that You sent me"; "I made known to them Your name and I will make it known"; "Yet you say that perfect knowledge is from the Spirit"; "But the things of the Spirit are Mine"; and "For if they learn who You are, then they shall know that I am not separated from You, but one of the greatly beloved, and a true Son, and closely knit to You. And those who are rightly persuaded of this, will keep both the faith which is on Me and perfect love; and while they love as they ought, I remain in them." Do you see how He has concluded the discourse with love, the mother of all blessings? Let us then believe and love God, that it may not be said of us, "They profess that they know God, but in their works they deny Him." (Titus 1:16)

References:
St. Augustine (On the Trinity III)
St. John Chrysostom (Homily 82 on the Gospel of John)