The Torah prohibits extracting juice from olives and grapes on Shabbat, as this constitutes mefarek (extraction), itself a derivative of dash. Just as threshing removes the grain from the chaff, so too the process of extraction removes the juice from the fruit.[1] Regarding other fruits, if it is customary in some places to squeeze them in order to drink the juice, then it is rabbinically forbidden to extract the juice on Shabbat. According to the Rama,[2] the prohibition applies only in places where it is customary to squeeze this fruit, whereas according to the Magen Avraham,[3] it depends upon whether the practice of squeezing this fruit would be widespread if it were plentifully available in more placesplentiful in more places. Many fruits, including grapefruits, oranges, strawberries, pomegranates, pears, tangerines, guavas, and others, thus fall under the rubric of the rabbinic prohibition. Fruits that are not regularly squeezed for their juice anywhere in the world may be squeezed.[4]
Regarding lemons, the Shulchan Aruch rules[5] that they may be squeezed. The Mishna Berura,[6] however, writes that since today it is very common to make lemon juice, it is likely prohibited to squeeze lemons for drinking. Indeed, the Rosh,[7] upon whom the Shulchan Aruch’s ruling is based, explains the leniency for lemons by noting that they are used for squeezing onto food. The gemara[8] says that one can squeeze grapes directly into a pot of food. Rashi explains that when juice is squeezed from a fruit directly onto a solid food, the juice is categorized as a food, not a liquid. Squeezing is considered extraction only when a liquid is removed from the fruit. Removing food from food is more like cutting the fruit into pieces than it is extracting. Most of the juice must be absorbed by the food for this leniency to be valid.[9]
Applying these rules, most poskim prohibit squeezing lemon into tea. Apparently, this holds even when the lemon is submerged and the juice is never a separate entity.[10] However, it is permitted to squeeze it onto fish. Most authorities permit squeezing lemon onto sugar, so that the juice is absorbed, and then adding the sugar to water or tea.[11] One may also put a lemon slice into a drink or into tea that is not too hot (less than 113° F or in a kli shlishi), allowing some flavor to ooze out without squeezing.[12] If the peel appears infested, it should be removed before putting the slice in the drink. (The Mishna Berura[13] reports a minhag to squeeze lemons directly into a drink since the juice is used only with other things. While not agreeing with the practice, he does not dismiss it entirely. Rav Ovadya Yosef[14] also upholds the Shulchan Aruch’s lenient ruling for Sephardim).