"Some talk that the devil hath a cloven foot; but whatever the devil's foot be, to be sure his sons have a cloven heart: one half for God, the other half for sin; one half for Christ, the other half for this present world. God hath a corner in it, and the rest is for sin and the devil." - Richard Alleine, as quoted in Spurgeon's Sermon Notes
Recommended reading:
The Forgotten Spurgeon, by Iain Murray
A Defense of Calvinism - by Charles Spurgeon