Scripture: Numbers 21:4-9
Current psycho-therapeutic reading of the story aside (which reminds me of a Jungian reading of John Bunyan's The Pilgrim's Progress which I disliked because of its ahistorical approach), a question that still stirs my pot is "why snakes?" Why not scorpions, lizards, grasshoppers, or any of a hundred different gift-cures God could have sent?
Assuming both God and the story-teller have a reason for a detail like this, it's worth noting the snake is a special animal in the ancient world.
Among the Hebrews, the snake appears at the very beginning in the Garden of Eden as that element of creation and of humanity at once wise and strong in its ability to reason and imagine as-yet-unheard-of scenarios of personal growth and achievement, and destructive of life in its unwillingness to observe and live within limits of trusting and mutually faithful relationship with others (including all creatures and God). The snake is part of God's good creation, but that part that is too slippery to be controlled and that constantly tests human willingness to learn, trust, and live within (rather than outside of, and against) God's good order.
Among other peoples, the snake was elevated to the level of a god. In Mesopotamia, the snake was both a fearful killer deity and a source of fertility -- be on the snake's bad side and you suffer; be on the good side and you prosper. Likewise in Egypt, the pharaoh's crown featured the head of a snake arching up and looking out from the ruler's forehead -- a clear and perpetual sign of who you needed to bow down to, if you wanted to be blessed rather than oppressed by the imperial power of the day.
The snake is the sign of any people who love to take the world into their own hands, and bend it to their benefit and well-being at the expense of others and of Earth itself.
And is that what's at the heart of this story in Numbers?
So far through the wilderness, God has answered the people's needs as they have arisen. But now it's not just a particular need the people are expressing; they are simply fed up with how long this is taking and that they don't yet have their promised land. They are tired of being a pilgrim people following a God who cares for them through a land they do not possess; they want to get to the promised land so they can start to be like other peoples.
It's a slippery slope, the first step of descent into the snake pit. So as a cautionary tale, God sends snakes to show them what it is they are choosing. The good life you want for yourself apart from others, divorced from the good of all the world will seem good, even somehow grown-up and right at first, but it will turn around and bite you as well. It will be the death of you, and the death of the world around you. (Oh my goodness, how current this seems!)
The people get the point (painfully so) and when they repent of their longing to be like the Joneses and the Egyptians and Mesopotamians, instead of making the snakes disappear (the snake really never is gone) God tells Moses to put a super-snake up on a pole so the people will not forget what they have learned, will be able to see the temptation of "the good life" for what it is, and will be healed in the remembering.