A major theme of פרשת כי תשא, is the holiness of Shabbat. After more than two Parshas that discuss the details of constructing the Mishkan, we are suddenly told, אך את שבתותי תשמורו, “But you shall observe my Shabbats.”
One of the immediate explanations of this Pasuk, is that although the construction of the Mishkan is a holy act, such work is not permitted on Shabbat.
The other important lesson learned from the positioning of this topic in the middle of the detailed instructions of the Mishkan, is the thirty nine מלאכות of Shabbat.
The activities that are forbidden to be done on Shabbat are all connected to the Mishkan.
Many of the מלאכות are the steps taken to bake the Showbread. Many others are related to preparing the curtains and covers of the אוהל מועד, tent of meeting.
It is always important to know the source for the Mitzvot we observe.