The Doctrine of the Trinity and the Source of the Christian Mission
Finally, we must notice that the doctrine of the trinity is the source from which the Christian mission flows. We have already observed that mankind was created to show forth the image of the triune God, as a diverse and yet unified covenant people, reflective of the diverse and complementary persons of the trinity. But just as our ontological existence as the people of God has its source in the nature of the ontological trinity, so our economical function as the people who are responsible to fulfill the Great Commission has its source in the economical trinity, by which the various persons of the Godhead undertook to accomplish the work of redemption.
In his high priestly prayer, Jesus explicitly relates the mission of the disciples to the mission that he himself had undertaken in pursuit of our redemption. Just as the Father sent Jesus, so Jesus has sent us. Just as the Son sanctified himself for his own mission, so he sanctifies us for our mission (see John 17:18-19). In other words, the economical functioning of the trinity is the source of the economical functioning of the Church of Christ, as she pursues the fulfillment of the Great Commission. This understanding may be fleshed out with a couple of further observations.
First, the redemptive role of the Son is the pattern for the economical functioning of the Church. Just as Christ suffered in his physical body to accomplish redemption, so now he is suffering in his mystical body to spread the effects of that redemption. In Colossians 1:24, Paul makes the stunning statement, â€œI am filling up in my flesh that which is lacking in the sufferings of Christ, in behalf of his body, which is the Church.â€ Just as Christ had to suffer in the flesh for the purchase of redemption, so now it remains for his mystical body to suffer for the spread of redemption. According to Paul, there is something lacking in the sufferings of Christ: it cannot be that any more sufferings are necessary to provide redemption; but there are more sufferings necessary to apply the redemption which has already been bought. It is necessary for the mystical body of Christ to suffer, or else redemption will not spread to all the people whom the Father has chosen.
This is because the sufferings of the believer are a necessary part of their witness, and so a necessary means for the fulfillment of the Great Commission. The proclamation of the gospel is the verbal testimony that tends toward the calling out of the elect; and suffering joyfully for righteousnessâ€™ sake, in the example of the Savior, is the dramatic representation of the gospel that tends toward the calling out of the elect. Both of these elements are necessary for the Christian mission. â€œThe blood of the martyrs is the seed of the Churchâ€ (Tertullian). It is only as the Church re-enacts the sufferings of Christ that the gospel will be powerful to spread throughout the earth. And so, in a very real sense, the functioning of the economical trinity is the necessary source for the advancement of the economical mission of the Church, that is, for the fulfillment of the Great Commission.
The second way in which the economical trinity is the source of the Christian mission is that, the same source by which the Son was guided in the accomplishment of his redemptive mission is now guiding the Church as she pursues her redemptive mission. Christ was sent out to accomplish the will of God, and it was the word of God that ever directed him as he he pursued his task. He did not reveal anything of himself, but brought the word of God to the men whom the Father had chosen. â€œThe words you gave to me, I gave to themâ€ (John 17:8); â€œI have given to them your word, and the world hated themâ€ (John 17:14). Similarly, the Spirit was sent to bring the word of God to his people (John 16:13). In the same way, the Church is set apart for her mission by the word of God. â€œSanctify them through your truth; your word is truthâ€ (John 17:17). In the economical trinity, Jesus was set apart for the mission of bringing the word of God to the people chosen by the Father, and the Spirit was likewise sent to bring the word of God to those people; but in the same way, the Church is now set apart for her mission by the word of God, and with the purpose of bringing that word to the world. The source which governed the redemptive tasks of the Son and the Spirit now govern the Churchâ€™s redemptive task of evangelization.
And not only is the source of direction the same in the economical trinity and the economical Church, but the source of sustenance and provision is likewise the same. Jesus, in the accomplishment of his redemptive task, was always guided and strengthened by the Spirit (e.g. Luke 4:1, 14, 18-21); and he was always sustained by prayer and fellowship with the Father (e.g. Luke 5:15-16). In the same way, the Church is accomplishing her mission only by the empowerment of the Spirit, and is sustained along the way through fellowship with the Father and prayer. Thus, the economical trinity, in particular the redemptive role of the Son, is the pattern, the source of direction, and the source of sustenance for the Christian mission today. -- from How the Doctrine of the Trinity Shapes the Christian Mission