(based on Ein Ayah, Shabbat 2:14)
Gemara: The pasuk [about the pit into which the brothers threw Yosef] says: "the pit was empty; it had no water." Considering it says that the pit was empty, don’t I know that it had no water? [It teaches us that] it did not have water, but it did have snakes and scorpions.
Ein Ayah: There are different categories of things that are damaging to people. Some things are made to be useful, but one can relate to them in a manner that makes them damaging to him. Instead of remedying such a situation by separation from the damager, one can just relate to it in its dominant positive side. The same is true for objects which can just as easily be used for benefit as for damage.
A pit full with water can cause one who falls in it to drown, but the pit is not objectively a damager, as it can easily be used positively – to provide water for those in need. An empty pit does not immediately have a positive use, but one does not need to remove it, as he can use it in the future for storing water. However, there is a pit to avoid – one which houses snakes and scorpions, which is unusable and damaging.
Chazal (Tanchuma, Vayigash 10) compare Yosef and Zion, as well as Yosef and Bnei Yisrael as a whole. Exile is sometimes referred to as a pit without water. Many thought that while Israel suffers from exile, exile need not be bad. Rather, they reason that our problems with exile stem from our approach and that if we learn to act in an endearing manner, the nations will accept us, and exile will become a stable life in a desired land. Such misguided people could view the pit (exile) as one with water, which is good as long as one is careful. However, their desire for the nations’ love is in vain. Not only is it not natural for exile to be a haven but even with efforts to make it livable (i.e., to live healthy Torah lives), they will not succeed because they will encounter damagers on all sides. Therefore, exile cannot even be compared to a pit without water, which can be filled with water. Rather it is like a pit with snakes and scorpions, which no one should want to be in, even after attempts to improve it. This curse of "and amongst these nations you will not have respite" (Devarim 28:65) also has an element of blessing, as it will cause Israel to raise its eyes to the Holy Mountain and the Desired Land.
There is a fundamental difference between the damage perpetrated by a snake and that by a scorpion, and this parallels our experiences in exile. A snake bites purposely, due to the enmity between our species, which began with Chava and the serpent; a scorpion will sting a man accidentally with its sharp tail. A snake loses its ability to attack for some time after biting; a scorpion can sting time after time (Yerushalmi, Berachot 5:1).
There were times that the nations tried to sever Bnei Yisrael from the Torah and our special status before Hashem. That can be compared to the purposely damaging snake bite. While they caused damage, their venom was weakened in the process. The more they attacked, the more we were aroused to cling to that which is holy to us, and people were willing to give their lives to sanctify His Name. About this, Chazal said, "that which I was hit caused me to be beloved by Hashem" (Vayikra Rabba 32:1).
Exile "stings" unintentionally due to its nature and the lowliness of Israel. The nation and then its leaders deteriorate over time in regard to purity, love of Hashem, and holy characteristics. This is because the exiles are affected by the prominence of the home nations in their own lands. Because the damage is stable and subtle, this "scorpion sting" is able to remain dangerous over long time periods. The positive factor is that danger’s longevity imprints on our national psyche that we should not think that exile can be good.
Historically, we learned from the story of Yosef, as well as of our patriarchs, that the pit of exile is not only empty from water but also full of snakes and scorpions. We have no choice but to get out of this pit as soon as we can.