In his epistle to the Christians in Rome, Paul exclaims,
But how are they to call on one in whom they have not believed?
And how are they to believe in one of whom they have never heard?
And how are they to hear without someone to proclaim him? (Romans 10:14).
Paul is describing the preaching of the apostles at the time of the very early church around A.D. 55, about 25 years or so following the death and resurrection of Jesus. The word Paul uses to describe apostolic preaching is keryssontos. The NRSV translates it as "someone to proclaim," and the NIV, "someone preaching." The most literal translation is "one heralding."
The apostles' primary task was preaching, but their preaching was a particular kind of preaching. Their preaching was heralding the Gospel of Jesus Christ, which Paul described as the good news "concerning [God's] Son, who was descended from David according to the flesh and was declared to be Son of God with power according to the Spirit of holiness by resurrection from the dead, Jesus Christ our Lord..." (Romans 1:3-4).
There is an old saying, "Tell me something I don't know." At the beginning of Christian history, the apostles were preachers who traveled around the world telling people something they did not know--that the Creator had raised Jesus from the dead by the power of the Holy spirit and declared him to be the Messiah of Israel and the world's true Judge and Lord.
In the days of the early church the main purpose of the preacher was to be a herald. A herald was someone who was authorized to preceed the coming of the king and to announce his arrival to the city. The apostles appropriated the role of the herald to announce the good news that our king, the Lord Jesus Christ, had arrived.
There was, of course, a need for other kinds of preaching--doctrinal, pastoral, ethical exhortation, and spiritual. But all preaching rested on the foundation of the apostolic heralding of the Gospel.
It seems to me that one of the characteristics of preaching during the long, now mostly gone, era of Christendom was a tendency to push the apostolic heralding of the Gospel into the background.
One day in my own ministry I suddenly realized that my preaching usually lacked the note of heralding the Gospel, except on high holy days such as Easter. The main opportunities for my congregation to encounter the original apostolic proclamation were in reciting the ecumenical creeds or offering the Great Thanksgiving during Holy Communion. (People who are members of churches where the creeds and ritual of the church are neglected are even more deprived of this encounter.) Yet, wasn't it a mistake to push what had originally been in the foreground into the background? I had not taken into account the people of this post-modern era who do not know the Gospel. I had been assuming that they might be in the house when they were clearly at the door of the church. So then, I changed course and tried to herald the Gospel in nearly every sermon, even if its purpose was not primarily proclamation, and even if the proclamation were brief. I sought opportunties to proclaim the apostolic message directly and fully. In other words, I discovered that preaching on this side of Christendom needed to be heralding the Gospel, not only to those who had never heard it, but also to those already in the church for whom it had become only the background of the life of the church.
Today there is a greater need for preaching which is heralding the Gospel more than any era since the first centuries of primitive Christianity. Even in the church where Christians already know the Gospel, there are many who have not heard it as news. The Gospel is not doctrine, but is news of what the Creator has done, is doing, and will do. Doctrine is the teaching of the church based upon the news of God's action in the world.
I admit this kind of preaching is different from having a conversation with the congregation. Conversational preaching has its place unless it compromises prophetic speech which announces God's action. The herald steps into the pulpit to proclaim news from God which turns the world and our lives upside down.
This kind of preaching requires broad and deep study of the Scriptures where the preacher enters regularly into the original arena of God's action in Israel and Jesus Christ in order to come forth to announce who God is and what God is doing in the world. This kind of study depends upon prayer since what God is doing requires the discernment only the Spirit of God can provide. Without study and prayer we preachers will be only clerks in the store of Christendom rather than heralds of the world's only true king and his kingdom.