Sefer Shemos concludes with the much anticipated completion of the Mishkan. Several Parshiyos were devoted to the details of its construction, how to craft the Kaylim and the order to its consecration. Yet, as we near the culmination of all these efforts, this weeks Parsha opens with Moshe gathering all of B’nei Yisroel together and warning them not to violate Shabbos, even for the purpose of building the Mishkan. After issuing this reminder, the remainder of Vayakhel and Pikudei are once again devoted to the building of the Mishkan. Why is it necessary to remind B’nei Yisroel of the sanctity of Shabbos at this time? We are not reminded of the prohibition of idol worship or any of the other “cardinal” sins here? Moreover, why in fact was Shabbos a more important commandment than the building of the Mishkan?
Understanding the Mitzvah of Shabbos and its origins help us better understand this quagmire. The Torah first mentions the concept of Shabbos in Sefer Bereishis, just after the creation of Adam and Chava. However in Bereishis, it is not conveyed as a commandment but rather as a reality. The Torah simply relates that after completing the works of creation, on the seventh day Hashem abstained from work. Hashem then blessed the seventh day and made it holy. (Bereishis 2:2-3) We are not told anywhere that Hashem gave a “Mitzvah” of Shabbos to Adam nor was it later incorporated into the Sheva Mitzvos B’nei Noach (the 7 universal commandments in which even Goyim are obligated) On the contrary, the Gemarah states that a goy who keeps Shabbos is deserving of death (Sanhedrin, 58b). Obviously, the “Mitzvah” of Shabbos was given only to the Jewish people.
This point is crystallized when Shabbos, for the first time, becomes a “commandment”. This takes place in Sefer Shemos when the “Mitzvah” of Shabbos is given specifically to B’nei Yisroel as part of the Aseres Hadibros. (Yisro, 20:8-9) There, B’nei Yisroel are commanded to “remember” the Shabbos and complete all their work in six days and rest on the seventh – because Hashem created the world in six days and rested on the seventh. (Yisro, 20:10) This stands in stark contrast to the second reading of the Aseres Hadibros where the “reason” given for the commandment of Shabbos is that Hashem took us out of Mitzrayim with an outstretched arm and therefore commanded us to keep Shabbos (Va’eschanan, 5:15) The different renderings of the Aseres Hadibros provide two distinct “reasons” for the commandment.
There is a Medrash Pliya which helps us answer all of these questions. The Medrash explains that through the first two millennia of the world, Hashem did communicate his desire for people to keep Shabbos. He communicated it to Nimrod and other leading people of the time. These leaders asked Hashem why they should keep Shabbos? Hashem responded that the reason was because He created the world in six days and rested on the seventh and it was His desire for us to emulate His conduct. To this, the leaders simply responded with “Nice story, but how do we know?” Who saw you create the world? By your own account, there were no people to see anything until the 6th day. After Yitzias Mitzrayim, the whole world knew of Hashem’s miracles and dominion. At that point Hashem said, “Remember that I took you out of Mitzrayim, I am the same God who created the world and rested on the seventh day.” It was only after Hashem revealed himself publicly at Kriyas Yam Suf that the heretics could no longer say “How do we know it was you”. Hashem’s Giluy Shechina at the Yam was specifically for this purpose – so that everyone would know, once and for all time, that it was He who created and ruled the world.
Accordingly it makes very good sense why the Mitzvah of Shabbos was reiterated at this point and why it “trumps” all other Mitzvos”.  Shabbos is the foundation of all other Mitzvos. It is fundamental in our relationship to our creator. It is Shabbos where we are instructed of Hashem’s desire for us to emulate His behavior. It is our Shmiras Shabbos which is indicative of our acknowledgment not only of Hashem taking us out of Mitzrayim but also of His being the creator of the world. It MUST trump the building of the Mishkan, honoring ones parents’ etc. because without Shabbos, we have nothing. The foundation crumbles.
From time to time we all look to take on something “extra” for a particular Segulah, perhaps for someone’s Refuah, for guidance or Hatzlacha. We really need never look further than our Shmiras Shabbos. There is no greater way to connect to Hashem and underscore the importance of our relationship to Him than by incorporating a Hiddur into our Shabbos observance. Thru this Zechus may we be Zoche to strengthen our bond with the Ribono Shel Olam and to see the Geula speedily in our days.
 Indeed, it is this prohibition, in this place, from which we learn the 39 Melachos which are forbidden on Shabbos. They are all directly related to “work” which was necessary for building the Mishakan.
 There are several reasons why one might think that the building of the Mishkan would “trump” Shabbos – e.g. There is a concept of Aseh Doche Lo Sa’aseh – a positive commandment supercedes a negative commandment and also the precept that Osek B’mitzvah Patur min Hamitzvah – one who is engaged in one Mitzvah is exempt from a competing one, etc.
 See Also, for example (Kedoshim 19:3) where we are also told that keeping Shabbos “trumps” a parallel commandment from the Aseres Hadibros of honoring ones parents.