The Israelites were grumbling against God, and God had enough. So God sent poisonous snakes and many Israelites died. Then they asked Moses their leader to pray for them.
Moses prayed for them and it is heard that God told Moses to make a bronze snake for the Israelites. He then made the bronze snake and put it up on the pole. An anyone that got bitten can look at it and be healed.
It is heard that an Israelite women, Mary had said," It is true! When I got bitten by a snake, I looked at the bronze snake and I got healed! "