Toil and excessive strain on Shabbos (“tircha”)
A restriction against excessive physical strain is implied in the words of the Navi (Yeshaya 58): “… And you shall honor the Shabbos in your goings, by refraining from pursuing your weekday occupations, and from speaking of them.” One may not exert himself for any non-Shabbos needs (even where the exertion involves neither melacha nor preparation for any post-Shabbos need), because this sort of activity is a detraction from the restful character and the honor of Shabbos. Any excessively strenuous activity that (due to the considerable exertion it requires) is only infrequently embarked upon, is prohibited on Shabbos for this reason. Example: One may not move or rearrange very heavy furniture or clean out his garage or basement, because this strenuous project is a detraction from the restful honor of Shabbos.
A) Tircha to prevent loss
In cases where a monetary loss can be prevented, some forms of tircha may be permitted. There are two categories of tircha in this regard:
1) Excessive Tircha to prevent loss
Excessive tircha involving non-Shabbos needs is forbidden on Shabbos event to avoid a loss.
Example: One may not drag furniture or heavy sacks of fruit indoors to protect them from frost, or cases of foods, pastries and the like, from a flooding basement.
2) Minor Tircha to prevent loss
Minor exertions to prevent monetary loss are permitted for even non-Shabbos needs, (according to most poskim).
Example: One may cover furniture that was left outdoors with a tarp or blanket to protect them from the rain or elements. (Note: Even muktzah items may be covered in this manner on Shabbos to protect them from damage.)
B) Tircha for Shabbos needs
Some forms of tircha are permitted for Shabbos needs. There are two categories of tircha in this regard as well:
1) Excessive Tircha
Major exertion is forbidden on Shabbos even for direct Shabbos needs. “Major” in this context might be defined as an activity that people would classify as a major project, i.e. a type of activity that one would ordinarily embark upon only with prior planning. Example: One may not move or rearrange very heavy furniture to redecorate a room for Shabbos.
2) Minor Tircha
Minor exertion or even small projects are permissible for the sake of a Shabbos need. “Minor” in this context might be defined as the type of effort characteristic in common everyday functions or spontaneous needs, i.e. something that one might suddenly need to do on any day without prior planning.
Examples: a) One may move aside heavy cases of wine etc. in his basement if this is necessary for him to gain access to something that he needs for Shabbos. (Note: Even muktzah items, e.g. bags of cement, sacks of potatoes etc. may be pushed aside by shoving them with one’s foot.)
b) Folding chairs and tables may be set up for a Kiddush on Shabbos if this could not be done before. If one requires the use of a heavy chair or table on Shabbos, it may be brought from one room to the next.
C) Tircha for mitzvah purposes
One may exert himself on Shabbos for the sake of a mitzvah.
Example: A room may be cleared of heavy furniture to make room for guests. (Note: Taking in guests – hachnasas orchim – is a great mitzvah!) Similarly, furniture may be moved around to make space for davening or for a Beis Midrash.