And the Lord said to Moses, Make an image of a snake and put it on a rod, and anyone who has been wounded by the snakes, looking on it will be made well. So Moses made a snake of brass and put it on a rod; and anyone who had a snakebite, after looking on the snake of brass, was made well.

Then they went on from Mount Hor by the way to the Red Sea, going round the land of Edom: and the spirit of the people was overcome with weariness on the way. And crying out against God and against Moses, they said, Why have you taken us out of Egypt to come to our death in the waste land? For there is no bread and no water, and this poor bread is disgusting to us. Then the Lord sent poison-snakes among the people; and their bites were a cause of death to numbers of the people of Israel.read more.
Then the people came to Moses and said, We have done wrong in crying out against the Lord and against you: make prayer to the Lord to take away the snakes from us. So Moses made prayer for the people.

He had the high places taken away, and the stone pillars broken to bits, and the Asherah cut down; and the brass snake which Moses had made was crushed to powder at his order, because in those days the children of Israel had offerings burned before it, and he gave it the name Nehushtan.

As the snake was lifted up by Moses in the waste land, even so it is necessary for the Son of man to be lifted up: So that whoever has faith may have in him eternal life.