Numbers 21:5-8

and spoke against God and Moses. They complained, “Why did you bring us out of Egypt to die in this desert, where there is no food or water? We can't stand any more of this miserable food!” Then the LORD sent poisonous snakes among the people, and many Israelites were bitten and died. The people came to Moses and said, “We sinned when we spoke against the LORD and against you. Now pray to the LORD to take these snakes away.” So Moses prayed for the people. Then the LORD told Moses to make a metal snake and put it on a pole, so that anyone who was bitten could look at it and be healed.