In the previous Halacha, we have learned that it is permissible to make ice on Shabbat.
The Gemara (Shabbat 51b) states: “Our Sages taught: One may not crush snow or hail on Shabbat; however, one may place it into one’s cup or dish and one need not be concerned.” This means that it is prohibited to crush snow, hail, or ice in order to turn the water back into its liquid form.
The Rishonim disagree regarding the reason behind the prohibition to crush snow on Shabbat: The Sefer Ha’Terumah explains that this is forbidden because of the Torah prohibition to create something new on Shabbat. Since crushing the ice turns it into liquid water, this constitutes the prohibition of creating a new substance on Shabbat. On the other hand, the Rambam, Ramban, and Rashba maintain that turning ice into water does not constitute a prohibition of creating something new, for this is not comparable to actually creating a brand new substance. Rather, the reason why crushing ice is prohibited on Shabbat is as a result of a rabbinic enactment prohibiting one to do so, for the act of crushing ice and turning it into a liquid is quite similar to the act of squeezing fruits and turning them into a liquid (squeezing fruits that are meant to be squeezed for their liquids, such as grapes and olives, is a Torah prohibition). Our Sages therefore forbade “squeezing” ice and turning it into a liquid. However, if the ice melts on its own inside one’s cup, this poses no concern at all.
Based on the above, according to most Rishonim including the Rambam, Ramban, and Rashba, the prohibition to crush ice on Shabbat is not because of the prohibition to create a new substance on Shabbat; rather, it is a rabbinic enactment because of its similarity to squeezing fruits. Indeed, Maran Ha’Shulchan Aruch rules in accordance with the majority opinion among the Rishonim that the reason for this prohibition is a result of a rabbinic enactment because of its similarity to squeezing fruits meant for their liquids. Nevertheless, the Rama rules that one must be concerned with the Sefer Ha’Terumah’s opinion that the reason for this prohibition is because one may not create a new substance on Shabbat. In the next Halacha, we will take this issue one step further and discuss whether or not one may use bar soap on Shabbat.