עברית
Halachot and Customs
Is it Permissible to Set an Alarm Clock on Shabbat?
Question
Can one set an alarm clock on Shabbat? It seems that one is allowed to turn off the alarm so it doesn’t ring until the battery runs out. Of course, this refers to a battery-operated clock with hands... Is the intention important? Does one need it to wake up early enough for Kriat Shema (the recitation of the Shema) or is it only for a man who wishes to get to the synagogue? Thank you for everything.
Answer
To the honor of the inquirer,
The halachic ruling of Rabbi Moshe Feinstein in "Igrot Moshe" (Orach Chaim 4:16) states that according to the Ashkenazi custom, following the opinion of the Rema, it is forbidden to activate an alarm clock on Shabbat if the sound is audible outside the room where it is located. (However, if the sound is not very loud and can only be heard in the room where the clock is, he also wrote that it is permissible).
However, Rabbi Ovadia Yosef, of blessed memory, [in a responsum cited in the book "Yalkut Yosef" (Shabbat 1, p. 95)] cited several later authorities who hold that it is possible to be lenient on this matter even according to the Rema. Furthermore, it should be noted that most people do not set the alarm every day to ring; rather, it is prepared each day to wake them from their sleep. In such a case, it is certainly not forbidden to activate the clock on Shabbat, as the poskim have written (as discussed in the Beit Yosef, Orach Chaim 338) that it is permissible to activate an alarm clock before Shabbat that rings loudly at all hours, since everyone knows that this clock has been prepared long beforehand, and it is not activated every single day, thus no prohibition applies at all.
All this only refers to the setting of the clock to ring - which must, of course, be done before Shabbat.
However, regarding disconnecting the clock or operating it and setting it on Shabbat, this is forbidden by all opinions, as is known, that any alteration to the electrical system of an electrical device on Shabbat is prohibited - even if the power is generated only by a battery.
Therefore, there is no permission to disconnect the ringing function on Shabbat when the ringing is produced by electricity coming from a battery.
To prevent the battery from running out, it is advisable to use a clock whose ringing lasts for a limited time and then stops by itself.
All this is permitted even if not for the purpose of a mitzvah - and thus the intention does not matter; all the more so if one uses an alarm clock for any mitzvah-related purpose, such as reciting Kriat Shema on time, which is allowed.
All the above refers only to the setting of the clock to ring being done before Shabbat; for it is forbidden to alter the clock's hands or the ringing mechanism at all from the time of Shabbat's onset.
Best wishes,
Rabbi Nachum
