'Preaching' in the Bible

For seeing that in the wisdom of God, the world through its wisdom didn't know God, it was God's good pleasure through the foolishness of the preaching to save those who believe.

My speech and my preaching were not in persuasive words of human wisdom, but in demonstration of the Spirit and of power,

If Christ has not been raised, then our preaching is in vain, and your faith also is in vain.