Is it permissible on Shabbat to separate food to serve it to somebody else? For example, may a mother remove edible food from an inedible substance in order to feed the food to her child? Assuming she follows the ordinary rules of Borer (separating on Shabbat) meaning, she takes the desirable food from the undesirable substance, and this is done by hand and for immediate use is this permissible, if she is not the one who will eat the food?
The Hida (Rav Haim Yosef David Azulai, 1724-1807), in his work Birkeh Yosef, rules that the rules of Borer apply equally to one who separates food for himself and one who separates food for somebody else. As long as one meets the standard conditions for allowing separating foods, this may be done even to feed another person. The Hida draws proof to this ruling from the Gemaras discussion in Masechet Shabbat (74a) of Rav Bibai, who was serving fruit to the Rabbis on Shabbat, and instead of serving each one individually, he placed the basket in front of them. The Gemara raises the question of why Rav Bibai chose this method, noting that this may have been done simply as an expression of generosity, so that each guest can take as much as he likes. However, the Gemara also raises the possibility that this was done to avoid the issue of Borer. Rav Bibai may have ruled that one may not separate on Shabbat even if he removes the desirable food from the undesirable food, and thus he could not selected fruits from the basket for his guests and had to bring them the entire basket, instead. It is noteworthy that the Gemara did not mention the fact that Rav Bibai would have been separating food for other people, and not for himself. It appears from the Gemaras comments that this was not a factor at all, proving that the standard rules of Borer apply regardless of whether one is separating for himself or for somebody else.
The Hida adds that this Halacha applies even if the person who separates the foods is unable to eat the food he is separating, such as if he had recently eaten meat and he is now handling dairy foods. Even in such a case, one may separate the foods for another person, as long as he follows the standard requirements of Borer.
This is the ruling of Sephardic Chief Rabbi Shelomo Amar, in his work of responsa, and this is, indeed, the Halacha.
Summary: The laws of Borer apply regardless of whether one wishes to separate food for himself or for somebody else. In both cases, separating is allowed if one removes the desirable food from the undesirable substance, and this is done by hand and for immediate use.
