Numbers 21:4-9 (ESV)

⁴ From Mount Hor they set out by the way to the Red Sea, to go around the land of Edom. And the people became impatient 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 we loathe this worthless food.” ⁶ Then the Lord sent fiery serpents among the people, and they bit the people, so that many people of Israel died. ⁷ And 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 And the Lord said to Moses, “Make a fiery serpent and set it on a pole, and everyone who is bitten, when he sees it, shall live.” ⁹ So Moses made a bronze^[a] serpent and set it on a pole. And if a serpent bit anyone, he would look at the bronze serpent and live.

John 3:14-15 (ESV)

¹⁴ And as Moses lifted up the serpent in the wilderness, so must the Son of Man be lifted up, ¹⁵ that whoever believes in him may have eternal life.^[a]