The weekly rest is commanded in the Ten Commandments in two different forms: Exodus grounds it in God resting after creation, Deuteronomy grounds it in the memory of slavery in Egypt, and rabbinic tradition treats both as equally binding rather than choosing between them. The Hebrew Bible gives few details of what the day required beyond not lighting fires and not gathering food, leaving later generations to work out its boundaries.
The Mishnah, compiled around the year 200, is where the well known thirty nine categories of forbidden labor first appear as a fixed list, derived by the rabbis from the kinds of work needed to build the Tabernacle in the wilderness, on the reasoning that the Torah places the two commands side by side. Centuries of later responsa literature extended those categories to technologies the Mishnah could not have imagined, electricity, automobiles, telephones, which is why observant households today debate elevators and timer switches using arguments built on a text two thousand years old.
The Reform movement, from the nineteenth century, rejected this expanding legal structure as binding while keeping the day as a spiritual observance, and Conservative Judaism developed its own, more permissive rulings on specific questions such as driving to synagogue. The result is a single biblical commandment observed today through three or more distinct, sometimes incompatible, legal traditions.