Ask the Rov: To visit a person in the hospital, a non-Jewish employee measures my temperature with a “gun.” Is this allowed on Shabbos?
By Rabbi Chaim Hillel Raskin – Rov of Anash in Petach Tikvah
Chazal prohibited any form of measuring on Shabbos or Yom Tov (see issue 361), precluding the use of even a non-electric thermometer.1 Measuring for health needs, or for a mitzva, is permitted, and one may measure fever with a non-electric thermometer.2
Regarding the use of electricity itself on Shabbos – independent of other possible melachos such as turning on lights or writing – there is dispute whether closing a circuit constitutes the melacha d’oraisa of boneh (building) or is prohibited mid’rabanan due to molid (birthing a new energy). Yet, the majority of contemporary poskim hold that it is d’rabanan.3
If an electric thermometer is d’rabanan, then having a non-Jew use it would be a shevus d’shevus, a double d’rabanan, which is allowed for great need or a mitzva purpose. A Jew may not perform the act himself, even a double d’rabanan for the sake of a mitzva.4
Is having one’s temperature taken considered taking part in the act?
Shluchan Aruch rules that if a tooth is causing you great pain, you can have a non-Jewish dentist remove it on Shabbos.5 Some explain that opening your mouth is only minimal assistance (mesayei’a), and the melacha is still being done entirely by the non-Jew.6 Others argue that even such a level of assistance forbidden; it is only permitted in cases that the Jew does not help at all.7 The Alter Rebbe follows the first opinion and permits any procedure that the non-Jew could do himself without the Jew preventing him.8
Poskim dispute if the exemption of mesayei’a applies by d’oraisa prohibitions as well, and in practice, we are lenient. Therefore, one who is slightly ill and needs a non-Jew to take blood is permitted to stretch out his hand.9
Although mesayei’a is permissible on a biblical level, Chazal prohibit it out of concern that one would come to do the melacha on his own. However, they lifted their decree in mitzva and health situations.10
Examples of qualifying mitzva purposes (for mesayei’a and shevus d’shevus) include to enable the performance of timely mitzvos like shofar, lulav or to transport important components of the Shabbos meal.11
In conclusion , having one’s temperature taken by a non-Jew can be allowed when it is truly needed or for a mitzva purpose.
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