What is the significance of the thick cloud (which was synonymous with the Arafel mentioned later [Rashi on 20:18])? Why did it have to be thick?
Rashbam: So that Moshe and the people should not look at the Shechinah.
Seforno: From Matan Torah and onwards, Moshe prophesied be mean of 'Ispaklaryah ha'Me'irah' (a clear vision), at this point, he had not yet attained that level, and he still prophesied via a thick cloud.
Why was it important for Yisrael to hear when Hashem spoke to Moshe?
Ramban #2: When they heard Hashem speaking to Moshe, they became themselves prophets.
Seforno: Since Yisrael witnessed firsthand that Hashem spoke to Moshe 'Face to Face', with all his faculties intact, they would believe that this was the level of Moshe Rabeinu's prophesies. 3
See Ramban, who maintains that Yisrael never doubted the institution of prophecy (Refer also to 19:9:3:1***).
Because up until now, the Avos, Moshe, Aharon and Miriam had prophesied by means of a vision or a dream, through the medium of an angel, and the people doubted that one could possibly prophecy whilst still in possession of all one's faculties. Now they knew that one can and that Moshe did (Seforno). This placed Moshe on a higher level than all the other prophets, negating the possibility of any other prophet to override his prophesies (Seforno). Refer also to 19:9:3:2***
Why did Hashem insert the word "v'Gam" in the phrase "v'Gam b'cha Ya'aminu Le'olam".
Ramban #1: Yisrael had now seen with their own eyes how Hashem had spoken directly to Moshe. 3 Consequently, they would now be convinced that Moshe Rabeinu's level of prophecy was superior to that of all subsequent prophets. 4
The question arises however, that on a number of occasions, the people did not believe the prophesies of Yirmeyah ha'Navi.
Thereby enabling them to refute any prophecy that negated that of Moshe (Refer also to 19:9:2:2**).
What did Moshe tell Hashem, and when?
Rashi: He told Him the people's response to Hashem's intent (to speak to Moshe), that they want to hear Hashem's words directly from Him, and not from Moshe. 1 He told Him this on the following morning (the fourth day - Thursday, the fourth of Sivan). 2
Da'as Zekenim (8), Riva: He reported the people's response in verse 8 ("Kol Asher Diber Hashem Na'aseh"). Moshe wanted to say this before (verse 8 - "va'Yashev Moshe Es Divrei ha'Am
Since one cannot compare hearing from the Shali'ach to hearing from the king himself (Rashi).
Seforno: When Yisrael answered "Kol Asher Diber Hashem Na'aseh" (in Pasuk 8), Moshe reported this verbatim to Hashem, and it was only after Hashem had explained to him in detail why He wanted him to act as the medium between Himself and Yisrael (Refer to 19:9:2:2) that he repeated their statement, because he thought that the people were afraid that his prophecy came via an angel, and that an angel does not have the authority to overlook their sins (See also Rashi, Shemos 23:20). So he repeated their response in that light.
Hadar Zekenim (8, citing Sefer ha'Gan): Moshe was afraid to speak until Hashem spoke first. A Talmid should not speak until his Rebbi speaks first. Moshav Zekenim: The protocol is, a Shali'ach does not report to the king until the king calls him. After Hashem spoke to Moshe, Moshe told Him the people's words.
Riva: Moshe told the people that night, and they answered that they accept Mitzvas Hagbalah. Moshe told this to Hashem the next morning.
The Torah does not record their response. (PF) Another version in the Gemara says oppositely
When did Moshe pass it on to Hashem?
Rashi: Moshe passed it on to Hashem the following morning (on the fourth day - Thursday, the fourth of Sivan).
Rashi writes that the people wanted to hear directly from Hashem. What is his source?
Riva: We infer from what Hashem said afterwards (verse 11), that Hashem will descend in the eyes of all the people.