There are 39 primary categories of work [forbidden on the Sabbath]. seeding, plowing, reaping, gathering, threshing, winnowing, sorting, grinding, sifting, kneading, baking, shearing wool, bleaching it, combing it, dyeing it, spinning it, mounting the warp of the loom, setting two heddles [in preparation to weaving], weaving two threads, unraveling two threads, tying a knot, untying a knot, sewing two stitches, tearing in preparation of sewing two stitches, trapping a deer, slaughtering it, skinning it, salting it & tanning its hide, smoothing [the hide], cutting the hide [into useful shapes], writing two letters, erasing in order to write two letters, building, demolishing, extinguishing a flame, kindling a fire, striking the final blow (completing production of an object), transferring an object from place to place. These are the 39 primary categories of work.