Numbers 21:7-9

7And the people came to Moses and said, We have sinned, in that we have spoken against Jehovah, and against thee: pray to Jehovah that he take away the serpents from us. And Moses prayed for the people.

8And Jehovah said to Moses, Make thee a fiery [serpent], and set it upon a pole; and it shall come to pass, that every one that is bitten, and looketh upon it, shall live.

9And Moses made a serpent of brass, and put it upon a pole; and it came to pass, if a serpent had bitten any man, and he beheld the serpent of brass, he lived.