Parshat Vayakhel (Shmot 35:1-3) begins with the words:

Moshe assembled the entire congregation of B’nai Yisrael, and said to them, “These are the words that God has commanded you to do. Work may be done six days, but the seventh day must be holy to you, it is a Shabbat Shabbaton for God. Whoever does work on it (Melacha) shall be put to death. You must not kindle a fire in all your dwelling places on the Shabbat day.”

B’nai Yisrael were already commanded to observe Shabbat when they received the Ten Commandments in Parshat Yitro, so why does the Torah teach us about Shabbat again in Parshat Vayakhel, a parsha which is primarily about building the Mishkan (Tabernacle)?

Rashi, who quotes the Mechilta explains that first God admonished them concerning Shabbat before commanding them about the works of the Mishkan, saying, in effect, that building the Mishkan does not supersede Shabbat.

Later in that same chapter in Parshat Vayakhel (Shmot 35:30-33) we read:

Moshe said to B’nai Yisrael, “See, God has designated by name, Betzalel, son of Uri, son of Chur of the tribe of Yehuda. And He endowed him with Divine spirit, with wisdom, with understanding, with knowledge and with skill to perform all types of crafting (Bechol Melacha) to devise plans (Lachshov Machshavot) with ingenuity, to execute those plans in gold, silver and in copper, in masonry for settings and in carpentry, to execute all kinds of clever tasks (Malechet Machshevet)…”

Many of the requirements necessary to consider an act a Biblical “Melacha” are learned from “Malechet Machshevet,” an act of craftsmanship, derived from the verses above.

We learn in the Talmud, Shabbat 49b:

A Braita taught that the 39 Avot Melacha (categories of work that may not be done on Shabbat) corresponds to the 39 labors of the Mishkan. One is only liable (Biblically) for a labor like which was performed in the Miskan. They planted, and likewise you shall not plant, they reaped, therefore you shall not reap etc.

In order for the Melacha to be considered Malechet Machshevet and forbidden from the Torah, one must have Kavana (intent) when doing it. If it was done accidentally, then it is not Malechet Machshevet. As well, the act must be constructive (Mitaken) not destructive. The act must be performed in the same way that it was done in the Mishkan (Tzricha L’Gufa). It must be done in the usual way (Kedarka). The act must cause permanent results (Mitkayem), not temporary. If the act can be performed physically by one person then it must be performed entirely by one individual in order for it to be a Biblical transgression.

We see from here that Malechet Machshevet is Biblically forbidden on Shabbat. In addition, the Sages added many Rabbinic prohibitions.