The quote to which you refer originates from Satan's temptation of Christ in the desert. Both Satan and Christ knew that God existed, so it was not a matter of trying to prove or disprove so. The context and purpose of the discussion was (a) Satan tempting Christ to cast himself down to the Stones (killing himself), inferring that all of the Angels in heaven would prevent Christ from dying (which, we see from the Crucifixion, was a false inferrence), and (b) Christ rejecting the lies and distortions which Satan made (the text which Satan quoted did not say what he implied it did, but was a distortion of the orginal meaning - kinda like what the liberals in the Methodist and Episcopal church are doing today).
The entire episode can be found in Matthew Chapter 4, 1-11. That was one of the THREE temptations brought upon Christ directly by Satan himself.
:) ttt
He will wipe the picture off the canvas and start over.