Here’s Kostenberger on Trinity and missions:

Rather than being one of several aspects or implications of John’s trinitarian theology, mission was shown to be the nexus and focal point of his presentation of the Father, the Son, and the Spirit, individually and in relation to one another. Hence it can truly be said, not only that John’s mission theology is trinitarian (which in and of itself is a significant statement), but that his trinitarian teaching is part of his mission theology – a truly revolutionary insight.

The insight is revolutionary because, if heeded, it calls the church to focus its major energies on acting on and acting out her Lord’s commission, “As the Father has sent me, I am sending you” (20:21), in the power of the Spirit, rather than merely engaging in the study of God or cultivating personal holiness (as important as this may be within the larger framework presented here). The insight is revolutionary also because a proper understanding of John’s trinitarian mission theology ought to lead the church to understand its mission in trinitarian terms – that is, as originating in and initiated by the Father (the “one who sent” Jesus), as redemptively grounded and divinely mediated by Jesus the Son (the “Sent One” turned sender, 20:21), and as continued and empowered by the Spirit, the “other helping presence,” the Spirit of truth.

…A comparison with Luke’s two-volume work, the gospel of Luke and the book of Acts, may prove instructional at this point. In essence, Luke, in his first volume, provides an account of the saving mission of Jesus culminating in his substitutionary cross-death and his resurrection. Yet, as Luke is careful to show, this is only the beginning. In his second volume, Luke narrates the coming of the Spirit…and the church’s Spirit-empowered witness “to the ends of the earth” (Acts 1:8).

It is our contention that John’s salvation-historical outlook is much the same as Luke’s, except that John accomplishes in one volume what Luke achieves in two. This lends John’s gospel a virtually unparalleled theological compactness and coherence. In John’s presentation, the Son is the focal point of the missio Dei in that he is the sent Son from God the Father, himself God, who also, together with the Father, becomes the sender of the Holy Spirit, who thus empowers Jesus’ followers for their universal witness.

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Andreas Kostenberger A Theology of John’s Gospel and Letters (Grand Rapids, MI: Zondervan, 2009) p. 545.

I want to do more theology like this!