In Genesis Chapter 37 Joseph’s brothers consider whether to kill him.
But Reuben heard, and he saved him [Joseph] from their hand[s], and he said, "Let us not deal him a deadly blow. And Reuben said to them, "Do not shed blood! Cast him into this pit, which is in the desert, but do not lay a hand upon him," in order to save him from their hand[s], to return him to his father… And they took him and cast him into the pit; now the pit was empty there was no water in it.
Rashi here reports an exposition from the Talmud (Shabbos 22a, Chagigah 3a):
Since it says: “now the pit was empty,” do I not know that there was no water in it? For what purpose did the Torah write “there was no water in it?” [To inform us that] there was no water in it, but there were snakes and scorpions in it.
The purpose of putting Joseph into the pit was to save his life. Naturally, this purpose would only be served by putting him into a pit which did not contain snakes and scorpions.
The exposition seems based on the issue of redundancy: the pit was empty and there was no water in it. But wouldn’t the more natural explanation be that the pit was empty – there were no snakes or scorpions, which would have been immediately fatal – and what’s more, there was also no water – which might have been dangerous too if the pit was wide, the water was deep, and Joseph was left there too long to continue to tread.
In other words, isn’t the exposition contrary to the plain meaning of the passage?