Just as Moses lifted up the snake in the desert, so the Son of Man must be lifted up.
Moses made an bronze snake, to be lifted up on a pole. Anyone who got bitten by snakes in the desert would be healed by just looking at the snake. The Messiah uses this example as a way to explain His own healing power, when He is lifted up. To use this verse as a defense of idol worship, is a deception. Because when the Jews started to burn and offer incense in front of the bronze snake, a Jewish King destroyed the idol to bring and end to such sin.