One of the critical conditions for permitting selecting on Shabbat is "L’altar"-for immediate use. That is, even if one fulfilled the other necessary conditions of selecting the Ochel (food) from the P’solet (waste), it must be done for immediate use. One application of this is setting a table on Friday night, after the meal, for the next day’s lunch. Is it permitted to select the forks or spoons from the mixture of silverware? Even if he selects the Ochel, i.e. the type of utensil he desires, it still is for the next day.
Rabbi Shlomo Miller has a novel approach to this question. He refines the definition of what is considered "L’altar"-for immediate use. Even though the primary use of the silverware is for eating, and that will only happen the next day, there is another, secondary, function of the silverware on the table, and that is "Yipui HaShulhan"-beautifying the table. When a table is set with the cutlery in the right position, the table, and the whole room, look nicer. Therefore, selecting the cutlery in order to immediately set the table is considered "L’altar" and is permitted the night before the meal.
However, this principle would not allow one to select a knife from a mixture of silverware in order to cut the roast on Friday night for tomorrow’s meal. He argues that cutting the roast is not a final function in and of itself; it is a mere preparation for the eating, which will only be tomorrow. Therefore, selecting the knife does not meet the condition of "L’altar" and is prohibited.
Similarly, Rabbi Miller analyzes putting together a puzzle on Shabbat from the perspective of Hilchot Borer (without getting involved in other potential Halachic issues). Sometimes, a person will select the pieces he needs, e.g. the corner pieces, from the pile. On one hand, this is Ochel from P’solet, but there is a potential problem of "L’altar." The main purpose of selecting pieces is to complete the puzzle. Since he does not always finish the puzzle on Shabbat, the selecting was done for a later date and is prohibited.
Rabbi Miller also rules that one should not play with a Rubik’s Cube on Shabbat. He argues that when one is trying to achieve a single color on one side, he moves the other colors to a different side. This constitutes selecting P’solet from the Ochel and is prohibited. Nevertheless, other Poskim may have a different, more lenient approach.
SUMMARY
It is permitted to select silverware from a mixture and set the table on Friday night for the next day’s meal.
