In John 3:14 Jesus references one of the strangest stories in the Bible and applies it to himself:
And as Moses lifted up the serpent in the wilderness, so must the Son of Man be lifted up (ESV).
The "lifting up" here clearly refers to Jesus's crucifixion. It is a well-known Johannine paradox that Jesus' sacrifice on the cross is presented as the exaltation and glorification of the Son. But what is the story of the serpent in the wilderness, and why does Jesus mention this story?
In Numbers 21 the people of Israel grumble once again against Moses and God. The sin of their faithlessness and ingratitude is exacerbated by the great signs and wonders they have been directly exposed to. As Rabbis have explained to me, Israel in the dessert is treated very harshly by God's justice because of the depth of sin needed to grumble, complain, rebel, doubt and stray to idols when they have themselves seen the parting of the Red Sea, the pillars of cloud and fire, and the exodus itself!
In this instance God responds by sending a plague of serpents of fire who bite the Israelites and make them painfully (and terminally) ill. Serpents of fire are a motif in ancient middle eastern sacred art and were some kind of spirit being (of a similar type to the seraphim in Ezekiel's vision, which were not angels of the type in the European imaginaire but winged serpents, probably having bodies of flame, as scholars of ancient middle eastern religion have shown). The burning serpents are therefore a kind of spirit being sent by God to punish the Israelites.
The story only gets stranger when Moses resolves the problem by following an instruction from God to make a bronze serpent (which would perhaps look firy in the burning sun of the desert) for the Israelites to gaze at and be cured. This object was actually preserved by the Israelites and later ended up becoming a focus of idolatrous worship (2 Kings 18:4).
Why does Jesus reference this story? One relatively simple explanation that lies ready to hand is the analogy with Jesus' crucifixion. Just as the ill Israelites in the dessert gazed at the serpent hung on the cross "and lived" so those sick with sin gaze at Jesus hung on the cross and live. It has also been pointed out that serpents represent sin in the Bible (Genesis 3:15) and Jesus "became sin" on the cross (2 Corinthians 5:10).
I think all of this is correct, but I recently came across another insight I wanted to share in a fascinating book by Rabbi Itzhak Shapira (The Return of the Kosher Pig). In order to understand R' Shapira's insight, we need first to understand the ancient Jewish practice of gematria.
Gematria is a type of Biblical exegesis which relies on a curious feature of Hebrew. In Hebrew there are no numbers. Hebrew letters are themselves numbers, so that aleph= 1, bet=2, etc.....
This means that any Hebrew word can also be read as a series of numbers. It is fairly common for Rabbis to use this fact to fish surprising insights out of the Bible by translating words into numbers and then seeing what other words or phrases contain the same numerical value. A popular example is the gematria of the divine name YHVH.
The numerical value of YHVH is 26, which it is often pointed out can be reached by adding the words echad (one, which equals 13) and ahavah (love, which also equals 13) together. As a side note, it is interesting that 1 Corinthians 13 contains 13 verses on love (13).
One can see how this kind of thing can get easily out of hand (and it does) yet sometimes insights gained through gematria can be quite illuminating and surprising.
Take the serpent. The Hebrew word for serpent, nahash, has a gematria of 358. This is the same as the gematria of the Hebrew word mashiach, or Messiah. Jesus avoids identifying himself as the Messiah directly throughout the Gospels, but a gematric translation of Jesus' words could be that the Messiah must be lifted up, hung on wood before the world, in order to give the lost life. Did Jesus intend this reading? What I find exciting about Rabbi Shapira's insight is that it is plausible that he did. Gematria is very old in the Jewish tradition. Even leaving aside for a moment the fact that God obviously knows gematria, my point here is that a 1st century Jew could be expected to know it. This means that Rabbi Shapira's insight may give us another insight, small but precious, into Jesus' mind.