"And the LORD said unto Moses, Make thee a fiery serpent, and set it upon a pole: and it shall come to pass, that every one that is bitten, when he looketh upon it, shall live." (Numbers 21:8)
This might seem an incredible story, but it was confirmed by none other than the Lord Jesus Himself: "As Moses lifted up the serpent in the wilderness, even so must the Son of man be lifted up: That whosoever believeth in him should not perish, but have eternal life" (John 3:14-15).
A plague of poisonous snakes had infested the camp of Israel, sent as a divine judgment because of their complaints and ingratitude, and many people had died. When they confessed their sin and Moses prayed for their deliverance, God in His grace prescribed this unique remedy.
There is, of course, no naturalistic process which can heal a deadly snakebite merely by a look. Neither, of course, is there a naturalistic explanation for the salvation of a sin poisoned soul merely by looking with faith upon the crucified Son of man. Both are mighty miracles, with the first being beautifully designed by God to be a prophetic foreshadowing of the other.
The symbolism is striking. The brass serpent impaled on the pole represented the poisonous serpents slain, but it also spoke of "that old serpent, which is the Devil, and Satan," eventually cast forever into the lake of fire (Revelation 20:2, 10). Thus it also symbolized the judgment on sin itself and its final banishment from God's creation.
All of this, however, was only the symbol. The real deliverance required Christ to be made "sin for us, who knew no sin; that we might be made the righteousness of God in Him" (2 Corinthians 5:21). The Son of man must be lifted up on the cross, and then all who see Him, and believe, receive life instead of death. HMM