Parshas Shelach

Rashi says that the story of the mekoshesh eitzim comes to tell us the downfall of Klal Yisroel. They kept the first Shabbos, but the second Shabbos they were mechalel. (Point to ponder; why was all of Klal Yisroel guilty of chilul Shabbos if only one person was guilty) The Mahral explains that Rashi saw from the Pesukim that the story happened when they were commanded about Shabbos. He asks how does Rashi Know that it happened the second Shabbos and not the first?
The 16th day of Iyar a Sunday, the Mon started to fall. That Friday the 21st of the month a double portion of mon fell and Yisroel was told of the hilchos Shabbos. The posuk tells us that on Shabbos Klal Yisroel went out to look for the Mon and they found none. The Marahal says it was that Shabbos that was the first one that Klal Yisroel rested and is the first time that the seventh day of the week is called Shabbos. Up until Parshas Beshalach- Parshas Hamon- there is no mention of the word Shabbos. The day only got the name Shabbos after klal Yisroel rested on that day. That is what Rashi means when they kept the first Shabbos- for had they not it wouldn't have been Shabbos at all. The first possible Shabbos that the story was able to take place was thus the second Shabbos.
What needs explanation is what does the term Shabbos mean and why was it only applied after Klal Yisroel rested?

The reason we have a Shabbos is to show our belief that Hashem created the world from nothing. The Bnie Noach are also obligated to believe in one G-d, so why is it a Goy that rests on Shabbos is punished by death?
The basic concept of the number seven s that every physical object has six sides- the seventh element is the inside- the hidden, that keeps it together. There are six day of the week and the seventh day- the belief in Hashem, is what keeps the world together. Every single society has a seven day week, nowhere in the world- to my knowledge- did they change that yet. For everyone has this basic belief ingrained in them. Klal Yisroels Shabbos is more then that. When we rest on Shabbos we connect to the source of creation- Hashem! Shabbos takes Klal Yisroel to 'Yom sheculo tov' out of the phyisical and into the world of Hashem. To that world the goyim have no connection. Up untill Klal Yisroel first forged that connection the seventh day was just that- the seventh day. No inherent kedusha, just the fact and belief that there is one G-d. When Klal Yisroel rested that first Shabbos they created a new reality- a reality called Shabbos, one that connects us to Olam Haba and the world of pure spirituality.