By Rabbi Yair Hoffman Introduction and Foundation The evolution of timekeeping devices has presented numerous challenges and considerations within Halacha, with each technological advancement bringing new questions to consider. Much of the following analysis is based upon information in a new article in the Ohalei Shabbos Gilyon 77-78 by Rabbi Yitzchok Rubin shlita and Rabbi Shalom Gelbar shlita. (My thanks to my brother-in-law, Rabbi Avrohom Hirsch, a prominent sofer in Yerushalayim who forwarded it to me). Early Mechanical Watches In the early 16th century, the development of mechanical watches revolutionized personal timekeeping through an intricate system of springs, gears, and the balance wheel. These early timepieces required daily winding to maintain their function by tightening the mainspring that powers the movement. The 1920s brought another significant advancement with the emergence of automatic mechanical watches, pioneered by British watchmaker John Harwood. These self-winding watches incorporated a weighted rotor that would swing with the natural movement of the wearer’s arm, automatically winding the mainspring and eliminating the need for daily manual winding, though this innovation presented new questions for Shabbos observance. The Battery-Powered Revolution The 1950s marked another milestone with the introduction of battery-powered watches. The Hamilton Electric 500, debuting in 1957, used a battery to power its movement instead of a mainspring. This technology later evolved into automatic battery-powered watches, combining traditional battery power with self-winding capabilities. Core Gemorah Principles The fundamental principles governing these matters derive from the Gemorah in Shabbos 48a, which discusses a case where Rav Chisda permitted returning padding to a pillow on Shabbos after it had fallen out. This ruling was challenged by a contradictory teaching which prohibited putting padding into a pillow or cushion. The Gemorah’s answer distinguishes between new padding, which is forbidden, and old padding that had fallen out, which may be returned. Rashi explains that the prohibition of inserting new padding stems from the biblical prohibition of making or fixing a vessel. This position was cited in the Mishnah Berurah (340:33), who notes that this carries a biblical prohibition. The Mishnah Berurah did not include the Rambam’s view (Chapter 22:23), which suggests the prohibition stems from a rabbinic decree to prevent one from sewing the pillow’s edges together. The Poskim’s Clarification The Poskim further clarified that the permission to return old padding only applies when it can be done easily without significant effort. This position regarding the effort involved in returning padding is found in Tosfos (Shabbos 48a) and the Mordechai (Shabbos 387), later cited by the Taz (317:4). From this halacha, the Poskim derived a broad principle: one may not perform a new assembly in a vessel, even when such assembly doesn’t involve the formal prohibition of building vessels. This principle led to practical applications, such as the prohibition of inserting a new shoelace into a shoe. However, if a shoelace that was previously threaded came out, it may be returned to the shoe. The Ran’s Commentary The Ran  (Shabbos 48a) states that it’s forbidden to transfer padding from one pillow to another. This would similarly apply to shoelaces. Rabbi Shlomo Zalman Auerbach zatzal concurred with this position, as cited in Shemiras Shabbos K’hilchasa (15:199). Inflatable Items Regarding inflatable items, halacha prohibits inflating rubber wheels or balls for the first time on Shabbos. However, if such an item was inflated at […]