Why did HaSh-m need to "go down, to see" what was going on in Sedom?
Rashi #1: To teach the Dayanim not to issue rulings in capital cases before seeing (whatever needs to be seen). 1
Rashi #2 and Targum Yonasan: What HaSh-m meant was that that He needed to delve into what their behavior will lead to 2 (to examine whether they were truly deserving of extinction, or whether they would perhaps relent and receive a smaller punishment 3 ).
Ramban (according to Kabalah): 'I will go down from Midas Rachamim to Midas ha'Din, and see with mercy whether they actually did like the cry that rose to Me from the Midas ha'Din, then they will be destroyed.
Seforno: To delve into their behavior, to determine the extent of their wickedness, and how low they would sink.
Lev Eliyahu (Bereishis, p. 57): This teaches that HaSh-m does not run the world according to His knowledge (that Avraham's Tefilah will not help, for there are not even 10 Tzadikim), rather, through cause and effect. He gave to Avraham a chance to pray for them.
Gur Aryeh: How is this derived from our verse? HaSh-m is all-knowing, even without descending to see. This verse is worded as such only to teach human judges that they must do likewise. Compare with Bereishis 11:5 regarding Migdal Bavel; refer to 11:5:1; refer to 11:5:1.1:1.
Presumably this too, was a lesson for the Dayanim, to do everything in their power to avoid the death-sentence, even when it seems obvious that the defendant is guilty.
Or get off without punishment (Targum Yonasan).
Which cry was HaSh-m referring to?
Rashi and Ramban (to 18:20): the cries of the oppressed that emanated from the entire city.
Rashi #2, Hadar Zekenim and Targum Yonasan: The cries of a girl 1 (Pleitis, the daughter of Lot) whom they killed in a most cruel manner for giving a poor man some food.
Seforno: What HaSh-m meant was that He would test them to see whether they would put their inherent evil into practice when Lot would attempt to rescue the angels from their hands; so that the world would know that their punishment was well-deserved.
Gur Aryeh: How does this explanation of the Pasuk differ from the first? According to the Sages, the word "ha'k'Tza'akasah" is in the feminine singular because it actually refers to one girl (not to a city).
What did HaSh-m mean when He said "Asu, Kalah," and " ... if not, I will know"?
Rashi and Rashbam: If they continue to rebel (against HaSh-m [Rashi]); If they did indeed behave in this way (Rashbam), HaSh-m will destroy them. 1 Otherwise, He will not destroy them, but commute their sentence to Yisurim (suffering).
Ramban (to 18:20): He will see for Himself if they all sinned, and if not, He will "visit their sin with a staff and their iniquity with plagues." 2
Seforno: He meant that the following incident will demonstrate how... they would all be guilty; not one person in Sedom would stand up for Lot! 3
Targum Yonasan: Refer to 18:21:1:2. But if they have done Teshuvah, they will be meritorious; it will be as if I did not know about their sins, and they will not be punished.
Moshav Zekenim: If they have no merit, I will finish them off. If not, I will afflict them.
Rashi, Rashbam: The line in between 'Asu" and "Kalah" indicates that there is a break between the two words.
Cf. Tehilim 89:33. HaSh-m was merely indicating that the final judgment had not yet been passed (in which case there was room for Teshuvah and Tefilah).
As the Pasuk will later testify (see Bereishis 19:4). The Seforno does not offer an explanation to the latter phrase. Presumably, he will explain it like the Ramban (Refer to 18:21:3:2).
Why didn't HaSh-m send a prophet to rebuke Sedom before destroying them, like He did for Nineveh?
Moshav Zekenim: He did! Lot told the people that the men (angels) were sent to rebuke us; they said "va'Yishpot Shafot" (we do not want this).
QUESTIONS ON RASHI
Rashi writes: "Alternatively - 'I shall descend [to examine] the end-result of their actions.'" But in this second explanation, Rashi does not explain the term, "and I shall see"?
Gur Aryeh: It goes without saying that "seeing" can also mean understanding (and not seeing in the literal sense). Rashi needs only explain that "descending" is also figurative, i.e. 'I shall examine their actions.' The first explanation, that "descending" is to be taken literally, explains "seeing" that way as well.
Rashi writes: "'Is it commensurate with its scream (ha'k'Tza'akasah)?' - ... of that province." What is Rashi explaining?
Gur Aryeh: The possessive is in the singular, although there were five cities. 1 Rashi explains that it refers to the one province that contained those cities.
Two of which were mentioned in the preceding verse (18:20), which is written in the plural, "their sin;" we would have expected our verse to be in the plural as well. (CS)
Rashi writes: "'They have done' - If they remain in their [state of] rebellion, 'I shall wipe them out.'" Why does Rashi add this?
Gur Aryeh: What did HaSh-m mean by His inquiry? We know from the preceding verse that in fact, it was so - "their outcry had become great, and their sin weighty" (18:20)! HaSh-m was asking if they now persisted in their rebellion by failing to do Teshuvah.
Rashi writes: "That is why there is a pause mark (Pesik) between 'they have done' and 'wiping out,' to separate those two terms."How else might we have read the Pasuk?
Gur Aryeh: We might have read it '[the people of Sedom] in their totality have acted so.' The pause indicates that they are two distinct phrases -' if they have acted so, then I shall wipe them out totally.'