This is a longer quote, but worth taking the time to read:
"I believe that those sermons which are fullest of Christ are the most likely to be blessed to the conversion of the hearers. Let your sermons be full of Christ, from beginning to end crammed full of the gospel. As for myself, brethren, I cannot preach anything else but Christ and His cross, for I know nothing else, and long ago, like the apostle Paul, I determined not to know anything else save Jesus Christ and Him crucified. People have often asked me, "What is the secret of your success?" I always answer that I have no other secret but this, that I have preached the gospel,—not about the gospel, but the gospel,—the full, free, glorious gospel of the living Christ who is the incarnation of the good news. Preach Jesus Christ, brethren, always and everywhere; and every time you preach be sure to have much of Jesus Christ in the sermon. You remember the story of the old minister who heard a sermon by a young man, and when he was asked by the preacher what he thought of it he was rather slow to answer, but at last he said, "If I must tell you, I did not like it at all; there was no Christ in your sermon." "No," answered the young man, "because I did not see that Christ was in the text." "Oh!" said the old minister, "but do you not know that from every little town and village and tiny hamlet in England there is a road leading to London? Whenever I get hold of a text, I say to myself, 'There is a road from here to Jesus Christ, and I mean to keep on His track till I get to Him.'" "Well," said the young man, "but suppose you are preaching from a text that says nothing about Christ?" "Then I will go over hedge and ditch but what I will get at Him." So must we do, brethren; we must have Christ in all our discourses, whatever else is in or not in them. There ought to be enough of the gospel in every sermon to save a soul. Take care that it is so when you are called to preach before Her Majesty the Queen, and if you have to preach to charwomen or chairmen, still always take care that there is the real gospel in every sermon."
-CH Spurgeon, The Soul Winner, p. 35