What is the significance of the juxtaposition of "Re'u Ki Hashem Nasan Lachem Es ha'Shabbos" to the previous Pasuk, "Lishmor Mitzvosai v'Sorosai"?
Yerushalmi Nedarim, 3:9: It teaches us that Shabbos is equal to all the Mitzvos in the Torah. 1
See Torah Temimah, note 43.
Why did Moshe say to the people "Re'u!"? What were they supposed to see?
Rashi: The fact that a double portion of Manna fell on Friday served as visual evidence that Hashem had sanctified the Shabbos and that they were not supposed to collect Manna on it.
Seforno: "Re'u" means (not 'See', but) 'Reflect' - that Shabbos is not just a Mitzvah, but a unique gift that Hashem gave to you exclusively. 1
Seforno: As the Gemara states in Shabbos (6b), and as we say in the Shabbos Amidah, 'And He did not give it to the nations of the world...' 'And Bnei Yisrael will keep the Shabbos, to make the Shabbos for all generations... in order to attain a day that is entirely Shabbos - Olam ha'Ba (Tamid 33b).
What are the connotations of the word "Shevu Ish Tachtav"? What was Moshe telling Yisrael?
Rashi #1: Tachtav" means four Amos in all directions. 1 And the Chachamim used this Pasuk to support the Din that allows someone who leaves the Techum Shabbos to carry up to four Amos from where he is standing. 2
Targum Yonasan: He was teaching the prohibition of carrying from one major domain to the other and of carrying four Amos in a public domain. 3
What did Moshe mean when he said, "Al Yeitzei Ish mi'Mekomo ba'Yom ha'Shevi'i"?
Rashi #1 and Targum Yonasan: It hints at the Din d'Rabanan prohibiting traveling beyond the Techum of two thousand Amos on Shabbos. 1
Rashi #2: Basically, Moshe was ordering them to remain in the camp and not to go out to collect the Manna on Shabbos.
Rashi (in the Beraisa of R. Yishmael): This is an example of 'Davar ha'Lameid mi'Inyano.' Seeing as the Parshah is talking about the Manna, which they had to travel two thousand Amos to collect, the Pasuk is issuing a prohibition against traveling more than two thousand Amos on Shabbos. 2
Rashi, ibid.: And not merely against moving from one's current location four Amos.
The Gemara in Eruvin 17b, learns from here that someone who travels outside the Techum on Shabbos is subject to Malkos, and the Chachamim argue over whether this applies to the Techum of two thousand Amos, or to that of twelve Mil, and two thousand Amos is only Asur mid'Rabanan. See Torah Temimah, note 45. See Torah Temimah, citing Eruvin 51a, which learns the Techum of two thousand Amos from a series of Gezeiros Shavos from Pesukim in Mishpatim and Mas'ei and note 47.
Why does the Torah write "Hashem Nasan Lachem Es ha'Shabbos" (in the past tense)?
Moshav Zekenim (in 5:4): When Moshe was in Pharaoh's house, Moshe convinced him that slaves will work better if they have a day of rest. And Pharaoh allowed Yisrael to choose a day, Hashem put into their heads to choose Shabbos. 1
