'Preaching' in the Bible

For the preaching of the cross is to them that perish foolishness; but unto us which are saved it is the power of God.

For after that in the wisdom of God the world by wisdom knew not God, it pleased God by the foolishness of preaching to save them that believe.

And my speech and my preaching was not with enticing words of man's wisdom, but in demonstration of the Spirit and of power:

And if Christ be not risen, then is our preaching vain, and your faith is also vain.