Take Heed Reaches Even the Rabbinic Boundaries of Rest

Yalkut Shimoni on Torah 355:2

Another interpretation: "And in all that I have said to you" and so forth (Exodus 23:13). Why is this said? Because it says, "You shall do no manner of work" (Exodus 20:10), from this I know only matters that are primary categories of labor; from where do I learn matters that are forbidden as a measure of rest [decreed by the Sages]? Scripture teaches, "And in all that I have said to you, take heed," to bring in matters that are forbidden as a measure of rest.

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