Is it permissible to squeeze a lemon on Shabbat, or does this violate the Shabbat prohibition of Sehita (extracting absorbed liquid through squeezing)?
The Shulhan Aruch discusses the laws of Sehita in the Orah Haim section (Siman 320), and presents a number of basic guidelines. First, the prohibition of Sehita does not apply to squeezing fruits directly over food. For example, it is entirely permissible, according to all opinions, to squeeze a lemon directly onto a salad, or onto Kibbeh. The law of Sehita refers only to squeezing a fruit over an empty utensil.
The question then becomes to which fruits the Sehita prohibition applies. It is clear that the Torah prohibition of Sehita applies only to grapes and olives, as these fruits are generally planted with their juices in mind. One who squeezes grapes over a cup to produce grape juice, or who squeezes olives into an empty container to collect oil, has transgressed a Torah violation, but this Torah prohibition does not apply to other fruits. It is also clear that the Sages enacted a prohibition against squeezing pomegranates or strawberries into an empty utensil. Squeezing these liquids is thus forbidden on the level of Rabbinic enactment. Hacham Ovadia Yosef, in his work Halichot Olam, rules that this Rabbinic enactment applies to oranges, as well. It is thus forbidden to prepare freshly-squeezed orange juice on Shabbat. Although some authorities permit squeezing oranges into a glass on Shabbat, Hacham Ovadia maintains that oranges have the same status as pomegranates and strawberries in this regard, and thus squeezing oranges is forbidden on Shabbat.
With regard to lemons, the authorities disagree as to whether they fall under the same category as pomegranates and strawberries with respect to Sehita. Some authorities claimed that lemon juice differs from other fruit juices in that it cannot be ingested on its own. It is ingested only as flavoring or when mixed with water, and therefore producing lemon juice by squeezing lemons would not, according to this view, constitute Sehita. This is the ruling of the Shulhan Aruch, and Hacham Ovadia Yosef, in his Leviyat Hen and in Halichot Olam, follows the Shulhan Aruch’s position. According to Hacham Ovadia, therefore, it would be permissible to squeeze lemons into an empty utensil on Shabbat.
However, most other Aharonim disagreed with the Shulhan Aruch’s ruling, and maintained that one may not squeeze lemons into an empty utensil on Shabbat. These authorities include the Hid"a, the Ben Ish Hai, Rav Haim Palachi, Rav Yaakov Haim Sofer, the Mishna Berura, and Rabbi Moshe Halevi (in his Menuhat Ahaba). Thus, for example, Rav Haim Palachi writes that if one wishes to prepare lemonade on Shabbat, he must first pour the sugar into the pitcher and only then squeeze the lemons over the pitcher. Interestingly, he writes that when preparing lemonade on Shabbat one should follow the sequence alluded to by the three letters of the word "Sulam" (ladder): "Sukar" (sugar), "Limon" (lemon), "Mayim" (water). According to Hacham Ovadia, however, it would be permissible to first squeeze the lemons into the pitcher, before adding the sugar or the water.
As for the final Halacha, it would certainly be preferable to follow the stringent view adopted by the majority of the Halachic authorities, and refrain from squeezing a lemon directly into a utensil. This is a situation where following the stringent view does not entail any difficulty, as one can easily squeeze the lemons directly onto the food instead of first squeezing them into an empty utensil. Therefore, although one who wishes to act leniently may rely on Hacham Ovadia’s ruling, it is certainly preferable not to squeeze lemons into an empty utensil.
Summary: It is permissible to squeeze fruit directly onto food on Shabbat. Certain fruits may not be squeezed into an empty utensil on Shabbat, and according to most authorities, lemons fall into this category. It is therefore preferably not to squeeze lemons into an empty utensil on Shabbat, though those who wish to do so have authorities on whom to rely.
