Numbers 21:4-9 (NIV) , Moses and the bronze snake: They (the Israelites) traveled from Mount Hor along the route to the Red Sea, to go around Edom. But the people grew impatient on the way; they spoke against God and against Moses, and said, “Why have you brought us up out of Egypt to die in the wilderness? There is no bread! There is no water! And we detest this miserable food!”
Then the LORD sent venomous snakes among them; they bit the people and many Israelites died. The people came to Moses and said, “We sinned when we spoke against the LORD and against you. Pray that the LORD will take the snakes away from us.” So Moses prayed for the people.
The LORD said to Moses, “Make a snake and put it up on a pole; anyone who is bitten can look at it and live.” So Moses made a bronze snake and put it up on a pole. Then when anyone was bitten by a snake and looked at the bronze snake, they lived.
Jesus said in John 3 (NIV): “Just as Moses lifted up the snake in the wilderness, so the Son of Man must be lifted up, that everyone who believes may have eternal life in him. For God so loved the world that he gave his one and only Son, that whoever believes in him shall not perish but have eternal life. For God did not send his Son into the world to condemn the world, but to save the world through him.”