"It is related of John Wesley that, preaching to an audience of courtiers and noblemen, he used the 'generation of vipers' text, and flung denunciations right and left. 'That sermon should have been preached at Newgate [prison],' said the displeased courtier to Wesley on passing out. 'No,' said the fearless apostle, 'my text there would have been, 'Behold, the Lamb of God which takes away the sin of the world.'" - Spurgeon's Sermon Notes
Further recommended reading & listening:
The Best of The Daily Spurgeon
The Forgotten Spurgeon, by Iain Murray
A Defense of Calvinism - by Charles Spurgeon