First a little background.
In the book of Bamidbar, Numbers, we find the story of when many Israelites were dying, because the sting of a serpent. As an interesting sidenote, the Hebrew rendering has them as flying fiery serpents. Most scholars and Jewish and Christian scientists now believe they were the now extinct pterosaur, but that's another blog entry.
In this story, God tells Moses to set up a Pole, with a Brass Serpent on it. God told Moses and the Israelites that whoever looked upon it would not die. Bottom line: The serpent on the pole did not save them, but their faith, in what God said, did. As a side note, please keep in mind, that it has always been taught that the serpent represented their sin and the brass was judgement. Together, they are judged sin.