According to Hashem's instructions, when should the Torah have been given?
Rashi and Targum Yonasan: Hashem instructed Moshe on the fourth of Sivan to prepare themselves for two days (the fourt and the fifth of Sivan) and that on the third day (the sixth of Sivan) Hashem would reveal Himself to the people and give the Torah.
What What is the significance of the preparations?
What is the meaning of "Vekidashtem"?
Rashi, Ramban #1 (citing Targum Onkelos) and Seforno: It means "Prepare yourselves". 1
Ramban #2 (citing the Ibn Ezra): It means 'Tovel in water'. 2
Ramban #3: It means "Sanctify yourselves" - by keeping away from your wives and from all kinds of Tum'ah. 3
As in Yeshayah, 13:3 (Ramban).
See Ramban's objection to this explanation.
Since someone who distances himself from Tum'ah is called 'Kadosh', as we find in connection with the Kohanim (See Vayikra 21:1). And this automatically entails Tevilah in a Mikveh - See Mechilta (Ramban). Refer also to 19:10:4:1.
What did the preparation entail?
Rashi and Seforno: It entailed separating from their wives (abstaining from intimacy). 1
Which became necessary now that they were about to attain (temporarily) a level pf prophecy 'Panim el Panim'. Refer to 19:9:2:2. And this explains why, after Matan Torah, Moshe was forbidden to remain with his wife. See Devarim, 5:27, 28 (Seforno).
Why did they need to wash their clothes?
Mechilta and Yevamos, 46b: Because whenever the Pasuk mentions 'Kibus Begadim', it means that there was Tevilah as well. 1
Yevamos, 46b: Because, if Tum'ah requires Tevilah where there is no Kibus Begadim, how much more so where there is. And we learn from here that a Ger requires Tevilah. Refer also to 19:10:2:3*.
Where and when was this Pasuk said to Moshe?