Numbers - Chapter 21

We read here the story of the bronze serpent on a pole lifted up by Moses.  The people were being killed by snakes, but when they looked at the serpent they lived.  Bronze represents judgement; the serpent represents sin; and sin being judged is lifted up on a wooden pole.

This is a prophecy of Jesus, and it is Jesus himself who makes this clear.  In John chapter 3 Jesus is talking with Nicodemus, and he says:

"As Moses lifted up the serpent in the wilderness, even so must the Son of Man be lifted up, that whoever believes in Him should not perish but have eternal life. For God so loved the world that He gave His only begotten Son, that whoever believes in Him should not perish but have everlasting life. For God did not send His Son into the world to condemn the world, but that the world through Him might be saved."