As the Lord lead Moses and the Israelites across the desert to the promised land, the people grew impatient. They complained and spoke against God and against Moses.
So, the Lord sent venomous snakes among them and many Israelites died.
Then the people cried out to Moses, “We have sinned against the Lord and against you. Please ask the Lord to take the snakes away from us.”
So, the Lord told Moses, “Make a bronze snake and put it up on a pole; anyone bitten and who looks at it will live.” And everyone who did so were immediately healed and lived.
So too the Jesus was lifted up on a cross, that whoever turns away from sin believes in Him may have eternal life.
Numbers 21:4-9