Resting From Plowing and Harvest Teaches the Sabbath Labors

"Six days you shall work, and on the seventh day you shall rest; in plowing and in harvest you shall rest" (Exodus 34:21). But were not plowing and harvest already included among all categories of work? Why then were they singled out? To tell you: just as plowing and harvest are distinct in that they are primary categories of labor [avot melachot] and one is liable for them on their own account, so too every other primary category of labor — one is liable for it on its own account. Another interpretation: "in plowing and in harvest you shall rest." Rabbi Shimon ben Elazar says: from the implication of "in plowing and in harvest you shall rest," you have a harvest that is a commandment, which overrides the Sabbath. And which is this? The harvesting of the omer. Rabbi Yishmael says: one might think that the plowing for the omer overrides the Sabbath; therefore the verse teaches "in plowing and in harvest" — a harvest whose time is fixed [overrides the Sabbath], excluding plowing, which has no fixed time. Rabbi Yehudah says: "in plowing and in harvest you shall rest" — plowing whose harvest is forbidden, this is the plowing on the eve of the Sabbatical year, and a harvest whose plowing is forbidden, this is the harvest after the close of the Sabbatical year. And Rabbi Shimon says: rest from plowing at the time of harvest, and rest from harvest at the time of plowing.