"When Satan looks at the Christian, and finds him faithful to God and to his truth, he considers him as we should consider a phenomenon - perhaps despising him for his folly, but yet marveling at him, and wondering how he can act thus. 'I,' he seams to say, 'a prince, a peer of God's parliament, would not submit my will to Jehovah. I thought it better to reign in hell than serve in heaven: I kept not my first estate, but fell from my throne. How is it that these stand?'" (Source: Spurgeon's sermon, Satan Considering the Saints)
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You can also listen to an audio recording of The Forgotten Spurgeon on Sermonaudio.com: