Thank you for this great forum!
The Torah tells us not to do melacha on Shabbos but does not gives us specifics as to what we shouldn’t do. Chazal tell us that whatever was done in the mishkan is forbidden for us to do on Shabbos. On a deeper level, what is the connection between what was done in the mishkan and the 39 melachos?
You are bringing an important point that we all need to know, in order to understand and have the correct appreciation for shabbos.
If we notice, the process of building the mishkan takes up a very large part of the torah. The torah elaborates tremendously, and is extremely specific, exactly how each vessel is to look, what material it is to be made from, and where it should be placed. This is not for naught, as we know that the torah does not waste words, and is written in a very concise way nevertheless when it comes to building the mishkan the torah goes into the very fine details. Why is this? Chazal taught us that all of the specifications regarding the building of the mishkan as told to us by H-shem, symbolically represented the various worlds, and that the mishkan was a microcosm of all of the universes, therefore it had to be build exactly according to specification because each of the dimensions, materials, and position of each of the vessels had to fit the specifications of the other universes. Chazal also tell us that when H-shem made man, He also made him a microcosm of all of the universes.
Just to give you an example of this, the sefer Ohel Yehoshua (Drush 1-12) elaborates how there were 613 parts to the mishkan, which represent the 248 organs and 365 sinews, in the human body, which represent the 248 positive commandment and 365 negative commandments. He also explains how the mishkan, in a way looked like a human body; the aron hakodesh represents the brain, which is the place the neshoma primarily rests. It is behind a paroches, and is separated- out of physical touch, the same as our brain- which is locked inside our skull and cannot be physically touched. On our bodies below the brain, come the two eyes and the nose, the two eyes being parallel to each other, and the nose placed lower down between the two. So too, outside the paroches was the menorah and the Shulchan, which were parallel to each other, with the mizbeach haketores a little further out, placed in between the two. Very much like a drawing of the human face. The mizbeach haketores was the place the incense was brought, which had a smell, representing the nose. A little lower than that is the mizbeach haolah, where the korbanos were brought, which represents our mouth. The korbanos were called “korbanei lachmei” my sacrificial bread. The idea being, that bread is what sustains our body and help our soul stay connected to our body and keeps us alive, so too the korbanos connect us to H-shem and keep us and the world connected to H-shem.
Getting back to our topic, when H-shem told the Jews to erect the mishkan he essentially was telling them to build a world. Erecting this world was done via 39 processes, that using human intellect, can manipulate the raw materials into a finished product, in this case the mishkan. Therefore in a way, the way to build the world is via these 39 processes.
After H-shem created Adam, he gave him dominion over the earth, and permission to develop it and manipulate it to his advantage. The way He gave Adam this dominion was not by making him the biggest or strongest of his creations, rather because He gave him intellect, and through that intellect, mankind can conquer and develop the world. This dominion is all through the39 melachos of intellect that man can use to manipulate the world. H-shem however told Adam that He is giving him dominion over the world for six days a week, however on the seventh day, he is instructed to willingly give H-shem back the “keys” to ruling the world, and that man should declare that the world belongs to H-shem. Therefore it is the 39 melachos, that built the mishkan, that we are instructed to abstain from doing, in a declaration to the whole world that the world really has a supreme boss and a creator, and whatever we do during the weekdays is only because He gave us the permission to do so.
Therefore it is specifically the 39 melachos that built the mishkan that we are commanded to abstain from doing in the shabbos.