The 39 Forbidden Shabbat Melachot
In parshat Trumah we begin learning how the Mishkan (desert tabernacle) was constructed. Many details of the Mishkan's construction are relevant for the future - they can guide us in preparing for the third Beit Mikdash, which we pray will be imminently built. But this knowledge is also relevant for the present. This is because of the intimate connection between keeping Shabbat and the construction of the Sanctuary.
In the Ten Commandments, we were forbidden to do "melacha" on Shabbat. We must desist from creative work on Shabbat to commemorate HaShem's desisting from creation on the seventh day. But the Torah did not reveal what acts constitute "melacha". Our Sages learned that the forbidden melachot are precisely those labors which were needed in preparing the Mishkan (Shabbat 73b). This seems to hint that in human terms, the building of the Temple can be compared to the creation of the world!
This comparison is elaborated by the Midrash, which explains that when HaShem created the world, He sought a "nether dwelling", so that His presence should rest even in the material world. The whole world was meant to be the sanctuary of the Holy One, blessed be He - a place for His presence to dwell.
But when Adam sinned God's presence was driven from this world, and the continued wickedness of subsequent generations drove the Shechina farther and farther away. However, the Patriarchs reversed this trend, and set in motion a process of drawing near to HaShem which culminated in the creation of the Tabernacle, which again restored His presence in the nether world. (Tanchuma Naso.)
We see that the construction of the Mishkan was intended to achieve the exact same objective as the creation of the world itself: to provide a place where HaShem's Presence could dwell within the material world. Indeed, the Tabernacle succeeded where the original creation failed, for since the building of this sanctuary HaShem's presence has never been completely driven from the world.
And for this very reason, the work of preparing the Sanctuary must cease on Shabbat. The Torah says "Keep My Shabbatot and be in awe of My sanctuary - I am HaShem" (Vayikra 19:30), and our Sages inferred that building the Sanctuary is forbidden on Shabbat. (Yevamot 6a.)
In this way we demonstrate that preparing the Tabernacle (or Temple) is a continuation of the work which HaShem began when He created the world - preparing a place where God's Presence can dwell among mankind. And just as HaShem desisted from His efforts on Shabbat, so we desist from ours.
But why does this compel us to rest from our ordinary everyday labors? The answer is that these labors also involve building a sanctuary! By relating these seemingly mundane labors to the work of the Mishkan, the halacha teaches that all of our weekday endeavors are ultimately directed towards making the world a fit place for God's presence. The spiritual repair of the world is intimately bound up with its physical repair. By pursuing our workaday concerns in accordance with the laws of the Torah and with the proper intention, we create an abode for Godliness in our surroundings.
Commemorating the Shabbat of the Creation by stopping work on the Mishkan shows that building the Sanctuary is a continuation of the work of creation; going one step further and basing the prohibition of everyday labors on the work of the Mishkan shows that these labors are a continuation of the work of the Sanctuary.
A Jew's weekday labors are not forbidden on Shabbat because they are so profane. On the contrary, they are forbidden because they are so holy - they are our way of turning the world into a sanctuary for HaShem. And these labors must cease on Shabbat, just as the work of building the Sanctuary ceased on this day, and as God's own work of creating the world ceased on the Shabbat. We interrupt our efforts to repair the world to remind ourselves that these efforts will eventually cease as they are crowned with success, on the future "day which is all Shabbat". We need to experience a bit of that future, in the form of Shabbat which is "like the World to Come", in order to properly prepare for it.