After the grievous sin of the golden calf, the Children of Israel seek a way to return to Hashem. Moshe brought down the second Luchot on Yom Kippur (the 10th of Tishrei), indicating that they were fully pardoned, but the people want more. They want every trace of their sin removed, their original relationship with Hashem restored.

The Mishkan was intended for this purpose of kapparah (atonement). Through building the Mishkan the people would achieve the return to Hashem they yearn for.

However, before beginning his instructions regarding the construction of the Mishkan, Moshe teaches the people the importance of Shabbat:
And Moshe assembled the entire community of the Children of Israel, and he said to them, “These are the things that Hashem has commanded to do them: For six days shall work be done, and the seventh day shall be holy for you, a complete Shabbat rest for Hashem; anyone who does work on it shall be put to death. You shall not kindle (T’VA’ARU) fire in all of your dwellings (MOSHVOTEICHEM) on the Shabbat day” (Shemot 35:1-3).
Here, Moshe repeats Hashem’s original instructions about observing Shabbat as stated in 31:12-17. The crucial work of the Mishkan will continue ceaselessly all week, yet it will be halted for Shabbat.

What is the meaning of specifying the Shabbat prohibition of:
You shall not kindle fire in all of your dwellings on the Shabbat day.
A number of answers are found in the sources, including:
• Kindling fire is singled out as an example, to teach that each principle type of work (av melachah) is separate. So if a person would, through ignorance, perform many prohibited acts during Shabbat, he would be obligated to sacrifice only as many sin-offerings as the number of avot melachah he violated (Yevamot 6b; quoted by Rashi).
• Fire is essential to the preparation of food, which the Torah permitted on festivals (12:16); on the other hand, the Torah emphasizes here that the preparation of food is forbidden on the Shabbat day (Ibn Ezra, Rashbam, Ramban; also Yerushalmi Beitzah 5:2).
• Kindling fire is accounted by the Torah as a melachah, even though it is destructive, whereas other melachot, derived from the building of the Mishkan, are constructive (Sforno).
• Kindling fire is prohibited only in your dwellings; however, in the Temple, where it is necessary to maintain the fire of the altar, it is permitted (Shabbat 20a).

One major interpretation of this verse, found in the Mechilta and Sanhedrin 35b, is enumerated by the Rambam as a mitzvah (Book of the Commandments, Negative #322)  that a court may not administer punishment on Shabbat. In the Laws of Shabbat 24:7 he explains:
Even though the punishment is a positive commandment, it does not override Shabbat. …You shall not kindle fire in all of your dwellings on the Shabbat day is a prohibition to the court not to burn on Shabbat one who deserves [execution by] burning, and the same law applies to other punishments.

However, the connection between the verse and the mitzvah-derivation seems remote, and requires explanation.

Haketav V’hakabbalah (R. Yaakov Tzvi Mecklenburg, 1785-1865) gives a detailed analysis of this verse, including a scientific explanation of the workings of fire, as well as some complex Talmudic issues. His main points are:
• Your dwellings (MOSHVOTEICHEM) can refer to the courts, because the verb
Y-SH-V often connotes “sitting in judgment,” with the connotation of “providing political stability,” as in For there they sat, thrones of judgment, thrones of the house of David (Tehillim 122:5).
• In execution, the burning is an end in itself, not only a preparation for some other action. The purpose of burning is to punish, and other forms of punishment accomplish the same purpose by other means.
• The verb B-A-R suggests both “burning,” as well as “removal, riddance,” as in Devarim 26:13. This reminds us of the repeated reason for all capital punishment,
And you shall remove (UVI’ARTA) the evil from your midst (Devarim 13:6; 17:7; 19:19; 21:21; 22:21,24; 24:7), or And you shall remove the evil from Israel (17:12; 22:22), or And you shall remove the blood of the innocent from Israel (19:13).
In essence, the verse thus commands: Do not, by means of any punishment, remove the guilty from the earth.

R. Mecklenburg concludes with a declaration of the stringency of Shabbat: Although offering the sacrifices and operating the Sanctuary will prevail over the laws of Shabbat, its holiness is not overridden, neither by the building of the Mishkan nor by punishing the guilty.

It is often said that building a “sanctuary-in-time” (Shabbat) is a higher priority than building a “sanctuary-in-space” (Mishkan). But, what of punishment, which is the duty of the court and brings atonement to the life of the criminal (Tosafot to Sanhedrin 35a)? Why does Shabbat supersede punishment?

Sefer Ha Chinnuch (ascribed to either R. Aharon HaLevi or R. Pinchas HaLevi of Barcelona, mid-13th Century) provides us with an analogy:
A great king summoned the people of the country one day to a feast, when he would not withhold entry from anyone, and after the day of the feast he would sit in judgment.

Shabbat is a day’s reprieve for all, a day without guilt or judgment, worry or punishment. On this day we are all equally the guests at the King’s table, for it is a day for us to find the forgiveness we seek.