Numbers 21:8-9

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.