Numbers 21:4-9

Then they set out from Mount Hor by way of the Red Sea to bypass the land of Edom, but the people became impatient because of the journey. The people spoke against God and Moses: “Why have you led us up from Egypt to die in the wilderness? There is no bread or water, and we detest this wretched food!” Then the LORD sent poisonous snakes among the people, and they bit them so that many Israelites died. The people then came to Moses and said, “We have sinned by speaking against the LORD and against you. Intercede with the LORD so that he will take the snakes away from us.” And Moses interceded for the people. Then the LORD said to Moses, “Make a snake image and mount it on a pole. When anyone who is bitten looks at it, he will recover.” So Moses made a bronze snake and mounted it on a pole. Whenever someone was bitten, and he looked at the bronze snake, he recovered.