The Son of Man Must Be Lifted Up
There are a number of things we could talk about in today's passage, as there are some unusual phrases and things that are a little hard to understand, but I'm going to deal with the final verses of today's reading. I'm doing so because the interpretation of the last part is quite certain, is key to the passage, and draws again on imagery from the Old Testament that we would miss if we're unfamiliar with the OT (which a lot of people are.
Jesus is referring in verses 14-15 to the events recorded in Numbers 21:4-9:
"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 serpent and set it on a pole. And if a serpent bit anyone, he would look at the bronze serpent and live." (ESV, emphasis mine)
***As a quick aside, I would like to mention how helpful "cross references" can be. In many Bibles you will see notes in the margins that include Bible verses that relate thematically to what you are reading about. A lot of people don't really use them at all, but this is a great example of how helpful they can be. In my ESV, there is a note in verse 14 that connects this passage to Numbers 21:9. As we've been talking recently about understanding the relationship of OT and NT, I would encourage you to be on the lookout for cross references. If there is a reference you don't understand (such as Jacob's Ladder or the bronze serpent) check for a cross reference to the OT and read the original story. You'll find it to be incredibly helpful in most cases. Back to today's post.***
From the NIVAC John commentary:
"Jesus then refers to a story from Numbers 21, in which Moses built a serpent of bronze and elevated it among the Israelites so that whoever gazed on it would be healed from the snakes that bit them in the desert. In the same manner, Jesus says, he must be 'lifted up' in order to become the source of eternal life for all who believe." 
I think that this event in the Old Testament is a foreshadowing event that points to Jesus as the ultimate picture and fulfillment, as He offers eternal life, not just deliverance from momentary death. We dealt with this concept when we read about the Transfiguration. For bonus points, does anyone remember the theological term for this kind of foreshadowing that is fulfilled in Jesus?