Exodus 20.11
For in 6 days Adonai made the heaven and the earth and sea and all that is in them, and ceased on the 7th day; therefore Adonai blessed the Sabbath day and hallowed it."
Talmud Shabbat 73a
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.
"From the Tradition" in Sparks Beneath the Surface (Rabbis Lawrence Kushner & Kerry Olitzky)
There are 39 kinds of work forbidden on the Sabbath. These are derived from the list of labors articulated in Exodus in teh midst of the building of the Tabernacle. Right in the middle of the work is the Veshamru text, in order to emphasize that even the building of the Tabernacle acts to conclude the story of creation (from which God rested) initiated in Genesis.
According to Rabbenu Bachya every kind of work is included in the prohibition against kindling fire. For it is well known that most of the work with which human beings occupy themselves is nothing more than one form or another of fire. Fire is the reason and the essence.
And it is for this reason that our sages ordained that we recite a blessing over the lights of fire during Havdalah at the departure of the Sabbath, since it is the commencement of the work of the six days of creation [which are about to begin again anew].
"Perush" in Sparks Beneath the Surface (Rabbis Lawrence Kushner & Kerry Olitzky)
On Shabbat, we consider the world to be complete. Just before Shabbat, with one fell swoop, we clear our desks of their clutter, and enter the completed world of Shabbat. fire, however, the only element note mentioned in the categories of prohibited work listed in the midst of building the Tabernacle, is puzzling for the commentator. Fire represents the primary factor in transforming one thing into another, such as matter into energy. It symbolizes all human activity. Thus, we cannot use fire at all, in any of its forms.
Talmud Pesachim 54a
Rabbi Yosei says: The thoughts of two phenomena arose in God’s mind on Shabbat eve, but were not actually created until the conclusion of Shabbat. At the conclusion of Shabbat, the Holy One, Blessed be He, granted Adam, the first man, creative knowledge similar to divine knowledge, and he brought two rocks and rubbed them against each other, and the first fire emerged from them.
My People's Prayer Book, Rabbi Lawrence A. Hoffman, Ed.
Lights of Fire. The Yerushalmi (PT Ber 8.6, 12b) relates this blessing to Adam. On the sixth day of creation, when Adam came into being, he could see from one end of the word to the other, using the primordial light that God had already created. But as Shabbat was ending, that light faded out and darkness fell. Adam, who had never experienced darkness, became afraid. To assuage his fear, the very next night God struck two flints together and made a fire. Adam was so grateful for this fire that he recited the blessing "Blessed...lights of fire." The third-century Babylonian Amora, Samuel, observes that since this first Shabbat after creation was the occasion of the first human use of fire, we mark it, as Adam did, by reciting the same blessing.
Havdalah blessing for lights of fire
Blessed are You, Adonai, our God, ruler of the world, creator of the lights of fire.
Havdalah blessing for lights of fire, The Book of Blessings, Marcia Falk
Let us seek the unseen sparks that kindle greater lights.