Many bronze serpents associated with temples dating to the period of Canaanite and Midianite occupation have been found in Israel. The significance of these cultic figures remains obscure, and it complicated by the fact that most surviving examples clearly represent cobras though the earliest examples are of snakes without hoods.
Nissim Amzallag proposes that earlier forms represent the painted carpet viper, a venomous species that invests the rocks and bushes of mountainous areas where copper was mined and smelted in ancient times. The most significant center of both mining and smelting of copper in the region was Punon, through which the Israelites passed in defiance of the the express prohibition of Edom (Numbers 20:14-21; 21:4-9; 33:5) and Yahweh's own warning: "Do not contend with them, for I will not give you any of their land, no, not so much as for the sole of the foot to tread on, because I have given Mount Seir to Esau as a possession" (Deuteronomy 2:5). The Edomites likely regraded carpet vipers as guardians of the shamanistic art of metallurgy, but what are we to make of Numbers 21:8, which states: "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'"?
Leaving aside the regional connection of snakes with smelting and furnaces with Yahweh, the simplest explanation is that the bronze serpent forces an association of the people's transgression with their restoration by the one who punishes them for their transgression, which is tantamount to recognizing the one against whom they have transgressed is God. This would seem to be the sense in which Jesus applies the image to himself:
No one has ascended into heaven except he who descended from heaven, the Son of Man. And as Moses lifted up the serpent in the wilderness, so must the Son of Man be lifted up, that whoever believes fin him may have eternal life. (John 3:13-15)
So Jesus said to them, "When you have lifted up the Son of Man, then you will know that I am he, and that I do nothing on my own authority, but speak just as the Father taught me." (John 8:28)
And I, when I am lifted up from the earth, will draw all people to myself. (John 12:32)
