Num Numbers, chapter Book of Numbers, chapter 21
The Israelites left Mount Hor by the road leading to the Red Sea so they could avoid traveling through the country of Edom. But the people became bad-tempered on the way and made complaints against God and against Moses, saying, “Why did you lead us out of Egypt to die in the desert? We don't have bread or water, and we hate this awful food!”21:5. “Awful food”: referring to the manna.
So the Lord sent poisonous snakes to attack them, and many Israelites were bitten and died.
The people went to see Moses and told him, “We were wrong to make complaints against the Lord and against you. Please pray to the Lord to get rid of the snakes from us.” Moses prayed to the Lord on their behalf.
The Lord told Moses, “Make a model of a snake and put it on a pole. When anyone who has been bitten looks at it, they will live.” Moses made a snake out of bronze and put it on a pole. Those who looked at it did live.