That is that He commanded us to rest on Shabbat. And that is His, may He be blessed, saying, "but on the seventh day you shall rest" (Exodus 23:12). And note that this commandment has been repeated several times. And He explained to us that rest from types of work is an obligation upon us and upon our animals and our slaves. And behold that the regulations of this commandment have been explained in Tractate Shabbat and [Beitzah]. (See Parashat Ki Tissa; Mishneh Torah, Shabbat 1.)

Six days you shall do your work, but on the seventh day you shall cease from labor, in order that your ox and your ass may rest, and that your home-born slave and the stranger may be refreshed.

Resting from labor on the seventh day fulfills a positive commandment, as [Exodus 23:12] states, "And you shall rest on the seventh day." Anyone who performs a labor on this day negates the observance of a positive commandment and also transgresses a negative commandment, for [ibid. 20:10] states, "Do not perform any labor [on it]."What are the liabilities incurred by a person who performs labor [on this day]? If he does so willingly, as a conscious act of defiance, he is liable for karet; if witnesses who administer a warning are present, he should be stoned [to death]. If he performs [labor] without being conscious of the transgression, he is liable to bring a sin offering of a fixed nature.

This fundamental mishna enumerates those who perform the primary categories of labor prohibited on Shabbat, which number forty-less-one. They are grouped in accordance with their function: One who sows, and one who plows, and one who reaps, and one who gathers sheaves into a pile, and one who threshes, removing the kernel from the husk, and one who winnows threshed grain in the wind, and one who selects the inedible waste from the edible, and one who grinds, and one who sifts the flour in a sieve, and one who kneads dough, and one who bakes. Additional primary categories of prohibited labor are the following: One who shears wool, and one who whitens it, and one who combs the fleece and straightens it, and one who dyes it, and one who spins the wool, and one who stretches the threads of the warp in the loom, and one who constructs two meshes, tying the threads of the warp to the base of the loom, and one who weaves two threads, and one who severs two threads for constructive purposes, and one who ties a knot, and one who unties a knot, and one who sews two stitches with a needle, as well as one who tears a fabric in order to sew two stitches. One who traps a deer, or any living creature, and one who slaughters it, and one who flays it, and one who salts its hide, a step in the tanning process, and one who tans its hide, and one who smooths it, removing hairs and veins, and one who cuts it into measured parts. One who writes two letters and one who erases in order to write two letters. One who builds a structure, and one who dismantles it, one who extinguishes a fire, and one who kindles a fire. One who strikes a blow with a hammer to complete the production process of a vessel (Rabbeinu Ḥananel), and one who carries out an object from domain to domain. All these are primary categories of labor, and they number forty-less-one.