"If salvation were partly of God and partly of man it would be as sorry an affair as that image of Nebuchadnezzars's dream, which was part iron and part clay. It would end in a break down." - 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