In Hilchot Mukse, there is a category of objects classified as "Kli She’melachto L’heter"-utensils designated for permissible activity. A classic example would be plates, books and food, since the use of these items is permitted on Shabbat.
The Gemara states that these items may be used for a broad range of functions. Specifically, they may be handled and moved for three purposes:
1. "L’sorech Gufo"-their primary purpose. For example, using a cup for drinking.
2. "L’Sorech M’komo"-for its place. If the item is in the way, it may be moved to make room for something else.
3. "Me’Hama L’Sel"-From sunlight to shade. That is, if the item was exposed to danger of being damaged or lost, it may be moved to safety.
Maran adds that within this category, food, drink and holy books are even more lenient and may be moved for no justification at all. The Poskim discuss what is the status of other items in this category, such as eating utensils, clothes and furniture. Is one permitted to randomly move a cup or chair, without one of the three purposes outlined by the Gemara? The Rambam (Hilchot Shabbat 25:1), as understood by the Magged Mishna, rules that these other items, besides food and books, need a justification to be moved. This is indicated by Maran as well in Siman 308:4, and this is also the ruling of Hacham Ovadia and the Ben Ish Hai (Rav Yosef Haim of Baghdad, 1833-1909).
On the other side, the Shilteh Giborim does not make a distinction between the items and rules that these items may be moved without any need whatsoever. The Mishna Berura (Rav Yisrael Meir Kagan of Radin, 1839-1933), in his primary ruling, agrees with this. The Menuhat Ahaba (Rabbi Moshe Halevi, Israel, 1961-2001) is also lenient.
Halacha L’ma’aseh, the practical conclusion is that one should be stringent and not move utensil and furniture for no reason. Only food, drink and books may be moved without a justification.
It should be noted that the Poskim give expanded definitions of what is a justifiable purpose in moving these items. The Hazon Ish (Rav Abraham Yeshaya Karelitz, 1878-1953) ruled that fidgeting with a fork to relieve nervous anxiety is also a valid justification. The Ben Ish Hai ruled that removing items from the table to make it more presentable is a valid justification, even though technically, the item was not in his way.
One can learn from this Halacha how serious the issue of Mukse is. Even "Kli She’melachto L’heter"-a utensil designated for permissible activity has restrictions on how it may be moved.
Food, drink and holy books may be moved on Shabbat for no purpose whatsoever, whereas eating utensils and furniture may only be moved for a distinct purpose.