As Moses lifted up the serpent in the wilderness, even so must the Son of Man be lifted up,
Moses lifted up the serpent ... refers to the last of Moses' miracles, which took place on the borders of Canaan  (Numbers 21:7ff).  Fiery serpents had been sent among the people producing suffering and death; Moses fashioned a serpent of brass and lifted it up on a pole in the center of the camp, and all who looked upon it were healed.