Numbers 21:6-9

And Jehovah sent fiery serpents among the people, and they bit the people; and much people of Israel died. And the people came to Moses, and said, We have sinned, because we have spoken against Jehovah, and against thee; pray unto Jehovah, that he take away the serpents from us. And Moses prayed for the people. And Jehovah said unto Moses, Make thee a fiery serpent, and set it upon a standard: and it shall come to pass, that every one that is bitten, when he seeth it, shall live. And Moses made a serpent of brass, and set it upon the standard: and it came to pass, that if a serpent had bitten any man, when he looked unto the serpent of brass, he lived.