The twelfth perek of Massekhet, which begins on today’s daf discusses and clarifies several of the thirty-nine categories of labor prohibited on. It concentrates on three categories of labor: Building, plowing, and writing. The categories of building and plowing were partially addressed in Chapter Seven. Our chapter mainly discusses two questions concerning these categories of labor.
First, what are some of the common subcategories [toladot] of these primary categories [avot], i.e., what are some specific activities included within the comprehensive definitions of the primary categories building and plowing? The definitions of these primary categories can be formulated in various ways, narrowly and precisely, or much more generally. They are comprised of many details, and the kinds of activities included within the parameters of each primary category must be clarified.
The second question in the chapter is how should the minimum measures that determine liability to bring this sin-offering, as defined by the Torah, be ascertained? With regard to the category of writing, there are additional problems: Is it necessary to specify the typical manner of writing, i.e., what form and what method constitute the creative act known as writing? Additionally, how do we determine the minimum act that can be considered writing? And, furthermore, does the definition of writing include any symbol or design, or is it limited to the reproduction of letters of the alphabet or other specific figures? And are all writing materials and methods of writing treated equally with reference to liability for performing this category of labor on?
The opening Mishna lists specific activities that all fall under the category of “building” on and the Gemara searches for the corresponding activity that took place in the Tabernacle that serves as the source for the prohibition.
In the Jerusalem Talmud a different approach to this issue is taken. There, the Gemara attempts to find the source for the primary category of building in the Tabernacle, rather than define the measure that determines liability for building. This is based on the fact that all of the measures are learned through tradition. According to what is stated in the Jerusalem Talmud, the building activity in the Tabernacle was the establishment of the beams. The problem is that the construction was temporary, which means it is less than ideal as the source for the primary category of labor. It is possible that this is the reason that in the Babylonian Talmud the Tabernacle’s construction is not cited as the source for the primary category of building.