Jesus’s promise and prayer define Christian unity in terms of what Trinitarian unity looks like, and Paul argues along the same lines when he calls on the body of Christ to demonstrate wholesome unity.

Jesus’s Prophetic Prayer

Jesus also drew an analogy between the mutual indwelling of the three persons in the Godhead and the unity that believers should share with one another:

Now I am departing from the world; they are staying in this world, but I am coming to you. Holy Father, you have given me your name; now protect them by the power of your name so that they will be united just as we are…. I am praying not only for these disciples but also for all who will ever believe in me through their message. I pray that they will all be one, just as you and I are one—as you are in me, Father, and I am in you. And may they be in us so that the world will believe you sent me. I have given them the glory you gave me, so they may be one as we are one. I am in them and you are in me. May they experience such perfect unity that the world will know that you sent me and that you love them as much as you love me. (John 17:11, 20–23)

Of course that’s an analogy not identical Trinitarian unity, because we cannot be exactly what God is in any respect. We’re God’s “image and likeness” but not members of the Godhead; nonetheless, just as the Lord calls us to act justly, to show mercy, even to be holy—“even as I am holy”—Jesus prays that we’ll live in mutual supporting union.

Paul’s Apostolic Exhortation

Paul spells it out in implicitly Trinitarian terms: “Make every effort to keep yourselves united in the Spirit, binding yourselves together with peace. For there is one body and one Spirit, just as you have been called to one glorious hope for the future. There is one Lord, one faith, one baptism” (Eph 4:3–5).

This unity isn’t generated by congenial relations within a naturally homogeneous social gathering; it’s supernatural unity provided by the Spirit. Nonetheless, Scripture charges us to nurture and practice it; so Paul calls on us to remember the Trinitarian nature of our calling. Just as a human body is animated by a single spirit, the church is a single body animated by one Spirit, headed up by one Lord, confessing one faith, sharing one baptism into Christ—“in the name of the Father, the Son, and the Holy Spirit”—and looking to one glorious hope.

Likewise, Paul reminded a fractious church in Corinth, “The human body has many parts”—exercising many gifts—“but the many parts make up one whole body. So it is with the body of Christ…. we have all been baptized into one body by one Spirit, and we all share the same Spirit” (1 Cor 12:12–13).

This is why, as we’ll see, God regulates and invigorates the gifts of the Spirit through the medium of the fruit of that unifying Spirit.