Numbers 21:9
And Moses made a serpent of brass, and put it upon a pole, and it came to pass, that if a serpent had bitten any man, when he beheld the serpent of brass, he lived.
Cross-reference
In 2 Kings 18:4, this very bronze serpent is destroyed by Hezekiah for becoming an object of idolatry.
Zechariah 12:10 speaks of looking on the pierced One—the same looking that brings salvation, prefigured by the serpent.
In John 3:14, Jesus explicitly compares his crucifixion to Moses lifting up the serpent—a direct typology.
In John 3:15, belief in the lifted Son of Man brings eternal life, just as looking at the serpent brought physical healing.
In John 12:32, Jesus being lifted up draws all people—echoing the lifting of the serpent that drew the afflicted to look and live.
In John 5:46, Jesus says Moses wrote about him — the bronze serpent is a key type of Christ lifted up for salvation.
Isaiah 45:22 calls all to look to God for salvation, paralleling the act of looking at the serpent to live.