When did Moshe pass on Yisrael's reply to Hashem's?
Rashi and Rashbam: On the following morning
- the second day (Tuesday, the second of Sivan).
Seeing as Moshe always ascended in the early morning (Shabbos, 36a [Rashi]).
When Hashem came to tell him that He was coming to him in a thick cloud (See Rashbam).
Why did Moshe find it necessary to bring Yisrael's response back to Hashem? Didn't He know it already?
Rashi #1: He is coming to teach us protocol, that it is good manners to return word to the sender, even if he knows the answer already.
Rashi in Vayikra (1:1): Hashem actually instructed Moshe to tell Yisrael what He said and to report back to Him.
Why does the Torah insert the word "Chol (in "Vaya'anu Chol ha'Am")?
Rashi (later, in Shemos 20:15): To teach us that there was not a dumb person among them.
Because every sick person among them was healed at Matan Torah. Refer also to 20:15:1:1). And by the same token, all the deaf were healed, which we learn from the fact that they all proclaimed "Na'aseh ve'Nishma!" (in Shemos 24:7 [Rashi Ibid.]).