The theological basis for this work of art of the "brazen serpent" is handed down to us in the fourth book of Moses in the Torah (the Hebrew Bible, often referred to in Christianity as the Old Testament). The New International Version (NIV) states: "The Lord said to Moses, 'Make a fiery serpent and hang it on a pole. Anyone who is bitten will live if they look at it.'" So Moses made a bronze serpent and hung it on a pole. If anyone was bitten by a serpent and looked at the bronze serpent, they lived. (Numbers 21:8-9)
In the New Testament, the evangelist John takes up this theme and reports a nighttime conversation between Jesus Christ and a Jewish scholar named Nicodemus. With the words: "And as Moses lifted up the serpent in the wilderness, even so must the Son of Man be lifted up, that whoever believes in him may not perish but have eternal life" (John 3:14-15), Jesus points to his impending crucifixion.