The idea of hachana is simple, but its practical parameters are difficult to define. One must not do actions in order to enhance his situation after Shabbat. However, if the action enhances Shabbat itself, it is permitted even if it enhances the weekday even more, provided that one does not do more of the action because of the weekday.[1]
When one finishes a meal, he usually has a few reasons to clear the table. In addition to preparing it for the next meal (which might be after Shabbat), most people are interested in a tidy dining room. Thus, one may clear the table. However, it is problematic to scrub the table or to do a thorough sweeping job if the room looks fully presentable for Shabbat. Similarly, if the dining area will neither be used nor seen until Shabbat’s conclusion, or if Shabbat is about to end, one needs other grounds for leniency.[2]
The Magen Avraham[3] and Mishna Berura[4] say that one may perform an action on Shabbat that in and of itself is permitted, in order to prevent damage to an object that is needed after Shabbat. Indeed, one is allowed to move a non-muktzeh item “from the sun to the shade” in order to protect it,[5] and halacha mentions no qualification that this is only when the owner might use the item on Shabbat. This is the main heter[6] for refrigerating leftover foods on Shabbat and even freezing them for later use.[7] In many cases, there is probably another reason for leniency. When one clears off the food, he has to find some place to put it. Since the refrigerator and freezer are as legitimate storage places as anywhere else, one has the right to store the food there, even if he also benefits from its use on a weekday. The heter of preventing loss is necessary only if the food is already removed from sight and one decides to put it in the freezer for longer-term storage. Shemirat Shabbat K’Hilchata[8] extends the leniency of preventing loss to instances where there is a legitimate concern that leaving food to spoil or crumbs on the floor will attract ants and other bugs.
There are two further innovative points of leniency at which Rav S.Z. Orbach[9] arrived, one of which dramatically expands the idea of preventing loss. Not only may one take steps to prevent a permanent loss, but he may also preserve a status quo from deteriorating even though the deterioration is easily rectified. Rav Orbach’s case in point is allowing one to soak dishes in water so that the residue will not harden, making washing dishes after Shabbat harder than it would be had they been washed right away. (This would not permit rinsing the dishes to remove residue, which is an additional action done to save time after Shabbat, not to preserve the status quo.) It appears that many previous poskim, including the aforementioned Magen Avraham and Mishna Berura, did not assume that this was the correct understanding of “preventing loss.”
A second idea, which is more compelling but for which it is hard to set parameters, is that actions that one does naturally under normal circumstances, without giving a second thought, do not constitute hachana. Let us offer some examples. One who returns sefarim to a bookcase as a matter of course after having finished using them may do so even if, in this case, that action has value only after Shabbat (e.g., a siddur after Mincha, a birkon after se’uda shlishit). Accordingly, one who regularly removes his utensils and leftover food right after eating may do so even after se’uda shlishit. One mustn’t say he is doing so to prepare for after Shabbat.[10]