They set up two computers with God looking on. Jesus and Satan both begin typing furiously for hours writing code, etc. Suddenly lightening strikes both computers, and Jesus and Satan lose all power.
Satan stares flabbergasted at his blank computer screen, while Jesus looks calmly around. Finally, the two of them power back up their computers, and Satan cries out in anguish when he realizes he has lost all his work. He turns to look at Jesus' computer screen and sees that his work has popped right back up on the screen, right where he left off. Satan turns to God and demands to know how it was that Jesus recovered everything, while all his work was lost.
God turns to Satan with a wry smile and simply says: "Jesus Saves!"