“The gospel is preached in the ears of all men; it only comes with power to some. The power that is in the gospel does not lie in the eloquence of the preacher otherwise men would be converters of souls. Nor does it lie in the preacher’s learning; otherwise it could consists of the wisdom of men. We might preach till our tongues rotted, till we should exhaust our lungs and die, but never a soul would be converted unless there were mysterious power going with it – the Holy Ghost changing the will of man. O Sirs! We might as well preach to stone walls as preach to humanity unless the Holy Ghost be with the word, to give it power to convert the soul.”
Charles H. Spurgeon On Preaching

"It was strictly forbidden to preach to other prisoners. It was understood that whoever was caught doing this received a severe beating. A number of us decided to pay the price for the privilege of preaching, so we accepted their [the communists' ] terms. It was a deal; we preached and they beat us. We were happy preaching. They were happy beating us, so everyone was happy."
Richard Wurmbrand Tortured for Christ

“A man who first tried to guess 'what the public wants,' and then preached that as Christianity because the public wants it, would be a pretty mixture of fool and knave”
C. S. Lewis Letters to Malcolm: Chiefly on Prayer