Preaching and the discipleship of the nations
How should we understand preaching in the context of the Great Commission?
In the New Testament the preaching of the Baptist, the Lord Jesus, the apostles and others is described by a wealth of terms. The most important are kerussein, "to herald," "to proclaim," euangelizesthai, "to publish good news," and didaskein, "to teach." They all carry a strong note of authority, especially the first term. This implies that the preacher has received his assignment and message from God; he does not invent it himself (Galatians 1); and he comes with the authority of his Sender.
Now the Great Commission was given originally to the Twelve, but since it would be absurd to think that they were able to reach to the whole world in their generation, then it is reasonable and logical to conclude that it was given to them as the foundational members and representatives of the New Testament church. As such the Great Commission is given to all the faithful.
The New Testament terms for preaching cannot be dissociated from the idea of the apostolate and its foundation in the arch-apostolate of Jesus Christ (John 20:21). This is especially true of the word used most often in John, marturein, meaning "to bear witness judicially as an eye-witness."
So preaching throughout the centuries up to this day is in a sense derivative from the testimony of the apostolic era, when these chosen men not only saw and heard Christ, even the risen Christ, but were also commissioned by Him to preach Him to all the world, and in Him preach repentance and forgiveness of sins, and continuing to build on this foundation by passing on in a lively manner all things that Jesus taught them.
The primary message of the apostles consists in a declaration of the redemptive-historical facts of Christ's life, His death, resurrection, session, and second advent, coupled with a call to repentance and faith. This proclamation is fundamental to the life of the church and the apostolic teaching which serves to build up the church.
The church has no warrant whatsoever to substitute preaching with some novel methodology, whether it be to indulge in experimentation or to attract a larger crowd. In the wisdom of God He not only commanded us what to teach (all things recorded in the Bible) but also the way by which we are to convey this sacred deposit to all hearers (by preaching).
So the Great Commission gives us the warrant to go, to be missionary-minded, and to pass on the truth of salvation to all; preaching is the divine method to be used by the church. "It pleased God by the foolishness of preaching to save them that believe" (1 Corinthians 1:21b).
We may be mindful to fulfill the Great Commission but end up using worldly means of communication; on the other hand we may be experts in preaching and yet end up preaching error and heresy. Both must be held to our view: conveying the truth of God through anointed preaching.