Question: May one sit on large stones on Shabbat? Similarly, may one lean on a car on Shabbat?
Answer: In the previous Halachot we have explained several laws of Muktzeh on Shabbat which are objects that our Sages prohibited moving on Shabbat for several different reasons. We shall now address the above question. Is one permitted to lean on or touch a Muktzeh object on Shabbat since by leaning or sitting on it, one is benefitting from the Muktzeh object and one may even come to move it slightly?
Regarding benefitting from Muktzeh on Shabbat, Halacha dictates that there is no prohibition to benefit from Muktzeh. Maran zt”l writes lengthily on this issue and concludes that although one may not benefit from an object which is “Muktzeh due to a Mitzvah”, such as an Etrog (citron) on the holiday of Sukkot (as we shall, G-d willing, explain at the appropriate time), nevertheless, one may benefit from regular Muktzeh which is prohibited to be moved on Shabbat.
Regarding touching Muktzeh on Shabbat, the Gemara in Masechet Shabbat (151a) tells us that the prohibition of Muktzeh does not only include picking up Muktzeh and moving it while it is in one’s hand; rather, one may not even bring about a situation where a Muktzeh object will be moved, even ever so slightly, for any slight movement is included in the prohibition of moving Muktzeh on Shabbat. For this reason, the Mishnah tells us that although one may take care of all of the basic necessities of a deceased person on Shabbat, nonetheless, one must take care “not to move any of the limbs,” for a corpse is considered “innate Muktzeh” on Shabbat, similar to wood and stones, and thus, one must be careful not to move any of its body parts. However, touching Muktzeh alone is not prohibited since touching is not considered moving Muktzeh in any way.
One may touch Muktzeh on Shabbat, such as a car or rocks, even though rocks are classified as “innate Muktzeh” and may not be moved on Shabbat (similar to any object which is neither a utensil nor does it have any particular use on Shabbat) and a car is certainly Muktzeh on Shabbat like any other “tool which is used for work forbidden on Shabbat” which may not be moved, as we have explained above. Since it is a Torah prohibition to drive a car on Shabbat, it follows that it will be prohibited to move a car from its current place in any way. Nevertheless, it is permitted to touch a car or rocks on Shabbat; thus, one may sit or lean on them on Shabbat.
Although when one leans on a car this causes the car to move slightly, nevertheless, this is still permitted since one is not actually moving it with one’s hands; rather, one is moving it “with one’s body” similar to pushing aside Muktzeh with one’s feet which is permitted on Shabbat based on the previous Halacha.
Summary: One may not move Muktzeh or cause Muktzeh to be moved, even slightly, on Shabbat. However, there is no prohibition involved in touching Muktzeh. Thus, one may sit on rocks or lean on a car on Shabbat although this causes them to move slightly.