Ask the Rov: Can I carry a gun in a holster on Shabbos in a locale that does not have an eruv?
By Rabbi Chaim Hillel Raskin – Rov of Anash in Petach Tikvah
On Shabbos, one is permitted to go outside wearing a garment (malbush) or ornament (tachshit). Wearing something outside that doesn’t fall under those two categories is a Shabbos violation.1
The Mishna records a debate about whether weapons are considered ornaments for a soldier. Rabbi Eliezer holds they are, but the chachamim disagree since they’ll be abolished when Moshiach comes. If they were truly adornments, they would be worn even when there is no longer any need for them. Halacha follows the chachamim, and if one wears them in the normal fashion — e.g., in a holster — one is liable min hatorah.2
For a soldier on active duty, some poskim posit that his weapons fall under the category of a malbush as they are part of his attire or are considered a tachshit for him.3 Of course, in a situation of active pikuach nefesh, carrying for safety purposes is absolutely permitted.
What about carrying a communication device outside?
R. Shlomo Zalman Auerbach was reluctant to allow doctors to carry phones in a bona fide reshus harabim, arguing that a doctor on call in such an area is required to stay at home and not go to shul. When heading to a patient in danger, he may carry his phone outside — with a shinui if possible (e.g., in his hat or socks) — or as an integral part of a “Shabbos belt.” If the area is a karmelis, the doctor may carry the phone with a shinui whenever he is on call.4
In cases that warrant this, some suggest wearing a smart watch with its own calling capabilities, which serves more clearly as a tachshit. To minimize its chillul Shabbos, any settings that aren’t needed should be turned off before Shabbos.
For the two-way radios (“walkie-talkies”) worn by Hatzalah members on call, R. Moshe Feinstein ruled in 5739 that they may wear it on Shabbos since it gives them a sense of respect and is considered a “tachshit” for them. Additionally, if Hatzalah members were forced to stay near their devices (i.e., at home), there is concern that fewer volunteers would agree to be on call for Shabbos.5
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From The Weekly Farbrengen by Merkaz Anash