Numbers 21:4-9 (NKJV)
Then they journeyed from Mount Hor by the Way of the Red Sea, to go around the land of Edom; and the soul of the people became very discouraged on the way. 5 And the people spoke against God and against Moses: “Why have you brought us up out of Egypt to die in the wilderness? For there is no food and no water, and our soul loathes this worthless bread.” 6 So the Lord sent fiery serpents among the people, and they bit the people; and many of the people of Israel died.
7 Therefore the people came to Moses, and said, “We have sinned, for we have spoken against the Lord and against you; pray to the Lord that He take away the serpents from us.” So Moses prayed for the people.
8 Then the Lord said to Moses, “Make a fiery serpent, and set it on a pole; and it shall be that everyone who is bitten, when he looks at it, shall live.” 9 So Moses made a bronze serpent, and put it on a pole; and so it was, if a serpent had bitten anyone, when he looked at the bronze serpent, he lived.