Shabbat 74 - What is selection?
One of the labors forbidden on Shabbat is selection, such as selecting rocks from a heap of grain. Regarding it, we learned a cryptic rule: "If one had different foods in front of him, he may select and eat, and he may select and leave for others to eat, and he may not select, and if he did select, he needs to bring a sacrifice."
Obviously, the four parts of the rule must all be talking about different situations to which each of it applies. Ulla explained, "He may select for this day and eat, but he may not select for the needs of the next day, because real selection is usually done for storage." Rav Chisda objected, "If one then allowed to bake for today?" Meaning, if it is a labor forbidden when done for tomorrow, how can it be permitted for today's needs? Rather, he can select less than the minimal amount of food, that is, a dried fig, but he may not do so for more than that.
Rav Yosef took issue with that, "How can it be allowed to performed forbidden labor in small amounts?" Rather, he is allowed to select with the hand, but not with an implement, such as a funnel. Rav Hamnuna challenged this also: "Does the rule mention anything about a funnel?" Rather, one can select good food and eat, but not bad food and leave it, similar to pebbles and grain! Abaye argued in turn, "Does the rule mention anything about good food and bad food?" Rather, he may select and eat immediately, or give to others to eat now; however, he may not select and leave for later, and if he did, it is as if he selected for storage, and that is prohibited.
In conclusion, the selection that is allowed follows all of the criteria: it should be for immediate consumption, selecting good for from the bad, and done with the hand. That, too, is subject to interpretation based on the order of how the opinions listed above combine.
Art: Eastman Johnson - Winnowing Grain