In John 3:14 Jesus said, "And as Moses lifted up the serpent in the wilderness, even so must the Son of man be lifted up" (King James Version)
When Jesus spoke of "the Son of man" He was referring to Himself. When He said that He must be lifted up, He was referring to His death on the cross to pay for the sins of the world. Three days later He arose from the dead to later ascend back into heaven.
Here is the account of the serpent in the wilderness:
Then the Lord sent fiery (burning) serpents among the people; and they bit the people, and many Israelites died. And the people came to Moses, and said, We have sinned, for we have spoken against the Lord and against you; pray to the Lord, that He may take away the serpents from us. So Moses prayed for the people. And the Lord said to Moses, Make a fiery serpent (of bronze) and set it on a pole; and everyone who is bitten, when he looks at it, shall live. And Moses made a serpent of bronze and put it on a pole, and if a serpent had bitten any man, when he looked to the serpent of bronze (attentivly, expectantly, with a steady and absorbing gaze), he lived. Numbers 21:6-9, Amplified Bible
Here is the words of Jesus in the gospel of John.
And Just as Moses lifted up the serpent in the desert (on a pole), so must (so it is necessary that) the Son of Man be lifted up (on the cross), In order that everyone who believes in Him (who cleaves to Him, trusts Him, and relies on Him) may not perish, but have eternal life and (actually) live forever!
John 3:14-15 Amplified Bible
