Dying in the desert
Israel was wandering in the wilderness. The people turned on God and on Moses, and death came into the camp:
"Wherefore the Lord sent among the people fiery serpents, which bit them, and killed many of them."
Numbers 21:6
They begged Moses to pray for them. God's answer was strange:
"And the Lord said to him: Make a brazen serpent, and set it up for a sign: whosoever being struck shall look on it, shall live. Moses therefore made a brazen serpent, and set it up for a sign: which when they that were bitten looked upon, they were healed."
Numbers 21:8 to 9 ยท around 1400 BC
No medicine. No ritual. Just look at the thing lifted up on the pole, and live.
Jesus explains it
Fourteen hundred years later, a Pharisee named Nicodemus came to Jesus at night. Jesus pointed him to this exact story:
"And as Moses lifted up the serpent in the desert, so must the Son of man be lifted up: That whosoever believeth in him, may not perish, but may have life everlasting."
John 3:14 to 15
Lifted up on a pole. Lifted up on a cross.
Why a serpent?
It seems backwards. The serpent is what was killing them. Why would the cure look like the curse?
Because that's what happened on the cross. The serpent is the first enemy in the Bible, the one who brought death into the world (Genesis 3). On the cross, Jesus took the curse itself and carried it:
"Him, who knew no sin, he hath made sin for us, that we might be made the justice of God in him."
2 Corinthians 5:21
The thing that killed them was lifted up and defeated. Everyone who looked at it lived.
Why this is a big deal
Jesus didn't leave this one for scholars to spot. He told Nicodemus himself: the serpent on the pole was a picture of him.
Fourteen centuries before the cross, God had Moses act it out in the desert. Lift it up. Look. Live.