'Preaching' in the Bible

For since in the wisdom of God the world by its wisdom did not know God, God was pleased to save those who believe by the foolishness of preaching.

My conversation and my preaching were not with persuasive words of wisdom, but with a demonstration of the Spirit and of power,

Instead I subdue my body and make it my slave, so that after preaching to others I myself will not be disqualified.

And if Christ has not been raised, then our preaching is futile and your faith is empty.