The Torah commands us to refrain from melakha on Shabbat: “But the seventh day is Shabbat of the Lord your God; you shall not do any melakha” (Shemot 20:9), that is, any of the 39 types of melakha done while erecting the Mishkan, as explained to Moshe at Sinai (see above, 9:1-2). The Sages added safeguards (“fences”) so that no one would do anything that might then lead to the violation of a Torah prohibition (see above, 9:3-4). There is an additional commandment in the Torah to rest on Shabbat: “Six days you shall do your work, but on the seventh day you shall cease” (Shemot 23:12). The point here is that in addition to avoiding melakha on Shabbat, we are also meant to cease and rest from toils and troubles. Thus one should not open his store or move heavy objects in preparation for the workweek. Even though these are not included in the 39 prohibited categories of melakha, nevertheless acting in these ways negates the mitzva of resting on Shabbat (Ramban, Vayikra 23:24; see MT 21:1 and the next section below).
Continuing with this line of thought, we find the prophets enjoining us to preserve the holy and sanctified atmosphere of Shabbat, a day on which one must avoid mundane activities. One who is careful to follow this merits great rewards, as Yeshayahu proclaims:
If you refrain from trampling the Shabbat, from pursuing your affairs on My holy day; if you call Shabbat “delight,” the Lord’s holy [day] “honored,” and if you honor it, and not go in your own way, nor look to your affairs, nor speak of them – then you will seek the Lord’s delight. I will set you astride the heights of the earth, and let you enjoy the heritage of your father Yaakov – for the mouth of the Lord has spoken. (Yeshayahu 58:13-14)
The Sages derive many guidelines about Shabbat from this verse, and the common denominator is that one should not behave on Shabbat as one does during the week. The Gemara elaborates:
“Honor it” – your Shabbat clothes should not be like your weekday clothes…. “Not go in your own way” – the way you walk on Shabbat should not be like the way you walk on weekdays. “Nor look to your affairs” – it is forbidden to look after your own affairs on Shabbat, but one may look after the affairs of heaven [i.e., religious matters]. “Nor speak of them” – your speech on Shabbat should not be like your speech on weekdays. Speaking [about mundane matters] is forbidden, but thinking about them is permitted. (Shabbat 113a).
These directives have a higher status than general rabbinic enactments since they are rooted in the Torah’s commandment to rest and are elaborated upon by the prophets.
We have already explained the mitzvot connected to honoring and delighting in Shabbat (chs. 2, 4, 5, 7). Honor (kavod) is expressed by wearing special Shabbat clothes, showering, cleaning the house, and lighting candles. Delight (oneg) is expressed by making Shabbat enjoyable through meals, sleep, and Torah study. In this chapter, we will explain the mitzvot and the rabbinic safeguards meant to protect Shabbat’s atmosphere as a holy day of rest. These mitzvot are at the root of everything that the Sages through the ages forbade as a weekday activity. Any activity that is unquestionably mundane is prohibited on Shabbat. This includes ball-playing for adults, swimming, working out, and bike-riding. To protect the spirit of Shabbat, the Sages also introduced the prohibition of muktzeh (as explained in the next chapter) and ordained that one may not play musical instruments (sections 17-19 below).
Even though the mitzvot to preserve Shabbat’s spirit and avoid weekday activity (uvdin de-ĥol) are of a higher status than the safeguards of the Sages, nevertheless the halakha is stricter in demanding adherence to the safeguards, such as the prohibition to do melakha with a shinui or to ask a non-Jew to do a melakha, which are forbidden even for the sake of a mitzva (as explained above 9:3-4, 11), whereas the prohibitions connected to preserving the spirit of Shabbat may be disregarded in the service of a mitzva (as explained below). There are some prohibitions that are comprised of both of these elements: if prohibited solely to preserve the spirit of Shabbat, it might have been permitted for the sake of a mitzva, but since the Sages decreed that it is prohibited, it remains prohibited even for the sake of a mitzva.