In biblical times, scraps of writing were stored together in jars, likely based on theme or topic, and these collections were combined and edited into our biblical books. Similarly, Talmudic pericopae began with collections of legal or wise sayings written on pitqi, “scraps,” and stored together in jars, or on a pinqas, wooden slats bound together.The observations in this essay make good sense to me as applied to the books of the Hebrew Bible, one of my areas of expertise.
I am not a Talmud specialist, but I have heard from other Talmudists that the Babylonian Talmud was largely orally transmitted for a long time, perhaps until as late as the tenth century. (See here, here, and here, although, regrettably, the relevant essay links have evaporated.) Dr. Amsler's work summarized in this essay points to the situation being more complicated.
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