Numbers 21:5-8

⁵And speaking against God and Moses, they said: Why didst thou bring us out of Egypt, to die in the wilderness? There is no bread, nor have we any waters: our soul now loatheth this very light food.

⁶Wherefore the Lord sent among the people fiery serpents, which bit them and killed many of them.

⁷Upon which they came to Moses, and said: We have sinned, because we have spoken against the Lord and thee: pray that he may take away these serpents from us. And Moses prayed for the people.

⁸And the Lord said to him: Make brazen serpent, and set it up for a sign: whosoever being struck shall look on it, shall live.