The Doctrine of the Trinity and the Goal of the Christian Mission
The most basic application of the doctrine of the trinity to the goal of Christian mission is simply this: if the inter-relationships of the ontological trinity are indeed covenantal, then the goal of Christian mission must also be covenantal. When God first created man, it was explicitly for the purpose of showing his own image. Man was different from all the creatures in the garden because he alone was created in the image of God (Genesis 1:26-27). When man fell and marred that image, Godâ€™s purpose was not frustrated: just as he had planned to show his image in creation, so he had planned to show his image even more fully in redemption. Not only did he create all things for his glory, he also engaged in all of his redemptive tasks for his own glory (see Isaiah 43:5-7); which is simply shorthand for the display of his own nature, which is eminently glorious.
What this means for the Christian mission is that, its ultimate goal is not simply to get as many individuals as possible off of the course of destruction, and into the bliss of heaven (as vital as that work of mercy is for displaying the character of a merciful God). On the contrary, it is all about reforming a new mankind, that will display Godâ€™s image in covenantal unity, even as the trinity exists in a covenantal love and unity. This is why, throughout the history of the Old Testament, Godâ€™s dealings with mankind were ever enacted on the basis of the covenants that he had inaugurated with them (see Genesis 9:8-17; 17:1-8; Exodus 19:3-6; 2 Samuel 7:12-16), and they ever involved the formation of an indissoluble and unified people of grace, and not merely a composite collection of persons of grace. God chose and saved the nation of Israel, not one person in ten from every nation of the world. And even now that he is expanding his kingdom to include every nation, he is still doing so by bringing representatives of every tribe, tongue, people, and nation into one new people, his own kingdom of priests (cf. Ephesians 2:11-22; 3:6; 1 Peter 2:9-10; Revelation 5:9-10).
This concept has at least three applications to the goal of missions: first, a Christian missionaryâ€™s task, when dealing with any unbeliever, is not just to get him a ticket to heaven, but to bring him into a covenantal relationship with God. Christ died, not so that we might sit on clouds with halos and strum our harps, but to bring us to God (1 Peter 3:18). The ultimate expression of the blessings of redemption is being brought into a covenantal relationship with God himself, which is substantially similar to the inter-relationship of the eternal persons of the trinity. Jesus died, by his own confession, to keep believers â€œin the nameâ€ of God (John 17:11-12). What that means precisely becomes clearer a little later when Jesus prays that they would â€œbe one in usâ€ (that is, in the Father and the Son â€“ John 17:21), and that he himself would be â€œin themâ€ (John 17:23, 26). The final goal of the Christian mission is to bring believers into a personal relationship with God which precisely expresses the personal relationships within the eternal trinity.
Second, the task of Christian missions is to bring believers into a mutual relationship with each other which in itself reflects the inter-relationships within the trinity. Throughout the epistles the virtue of Christian unity is espoused and urged more than almost any other virtue (e.g. Ephesians 4:1-6; Philippians 1:27; 2:1-5). Believers show forth the divine, inter-trinitarian image when they are united in a diverse, loving, and mutually-honoring covenantal relationship.
Third, the goal of the Christian mission is ultimately to glorify God. If believers are to be perfectly happy, it is only to be by entering into a state similar to that of the perfectly blessed (i.e. happy) Godhead (e.g. 1 Tim. 1:11; 6:15). True Christian joy reflects the state of unruffled blessedness that has always existed in the trinity, the persons of which bring constant and illimitable joy to each other unceasingly. Therefore, it is a joy which is primarily designed to glorify God, that is, to display the nature of God. In other words, as great as are the blessings which God has given to followers of Jesus, those blessings themselves serve the greater purpose of glorifying God. God accomplished his work of redemption in order â€œto showâ€¦the riches of his grace in kindness towards us in Christ Jesusâ€ (Ephesians 2:7). It was â€œto make known the riches of his glory in vessels of mercy, which he prepared beforehand unto gloryâ€ (Romans 9:23). Thus, any expression of the goal of the Christian mission which stops short with the needs of the unbeliever is essentially inadequate. Missions exists to bring eternal joy and life to sinners, but only because that will bring eternal glory to God, by displaying his nature in those whom he saves. -- from How the Doctrine of the Trinity Shapes the Christian Mission