Why is the word "va'Yikachuhu" missing a 'Vav' (after the 'Ches')?
Ba'al ha'Turim: Because it was only Shimon who actually took him and threw him into the pit. 1
Which explains why it was Shimon that Yosef later placed in jail. Refer also to Bereishis 42:24:2:1, 42:24:3:1*.
Why did the brothers throw Yosef into the pit?
Ramban and Seforno: Refer to 37:22:3.
Oznayim la'Torah: They actually accepted Reuven's suggestion, and threw Yosef into the pit in the interim until they decided what to do with him. 1
Ha'amek Davar: They did not push him in from nearby, for this could break his leg! Rather, they lifted him and lowered him until the floor of the pit.
Oznayim la'Torah: Since leaving him in the pit from which he could not extricate himself would have constituted murder - See Sanhedrin 77 - and they had decided not to murder him. This is also implied in 37:28.
Having said that the pit was empty, why does the Torah add that it contained no water?
Rashi: For the inference - that it contained no water, 1 but it did contain 2 snakes 3 and scorpions. 4
Ramban #1 (to 37:22) and Rashbam: The Torah tells us that the pit was not full of water, because if it had been, having decided not to kill him directly, they would not have thrown him into it to drown. 5
Ramban #2: To emphasize that there was not even a small amount of water in it. 6
Ha'amek Davar: It was empty of rocks, on which his head could get bashed, and of water in which he would drown. 7 That would be like overtly killing him!
Divrei Eliyahu: Mayim alludes to Torah. One who has no water (Torah) is prone to have snakes and scorpions, i.e. despicable Midos like snakes and scorpions.
Da'as Zekenim, Hadar Zekenim: Two exclusions (Rek, Ein Bo) always come to include. Do not say that it contained rocks, for "Rek" implies something that it is sometimes Misroken (emptied) of. Snakes hide in cracks (leaving the pit usually empty). (Compare to Gur Aryeh 37:24:2.1:1.)
Hadar Zekenim, Moshav Zekenim: We read "Yeshevu Le'echol Lechem" (37:25) like 'Yesh Bo Le'echol Lechem' (there is something inside that can eat; Rosh - there is something edible inside). Moshav Zekenim, Ba'al ha'Turim - Alternatively, we learn a Gezerah Shavah from the verse, "Nachash Saraf v'Akrav, v'Tzima'on Asher Ein Mayim" (Devarim 8:15).
Ramban: The brothers, however, were unaware of this.
Refer to 37:24:2:4*.
Since that would have caused Yosef more suffering than he was destined to suffer. Refer to 37:25:2:2. (EC)
Even if the pit was too narrow to swim properly, Yosef could tread water! Granted, one can do so only for a limited time. Why is this worse than leaving him to starve, which is considered only Gerama? This requires investigation. (PF)
QUESTIONS ON RASHI
Rashi writes: "... It did not have water... but it did have snakes and scorpions." But perhaps what it did have was sticks and stones?
Gur Aryeh: If there were sticks and stones in the pit, it would not be called "empty." Snakes and scorpions do not fill a pit, because they remain for a short time, and then leave. 1 As such, it was still empty.
Gur Aryeh: But had the verse written only "the pit was empty," I would have thought it was empty of everything that might have harmed Yosef, be it water or vermin.