QUESTION: Why is the custom to light Shabbos candles eighteen minutes before shkia (sunset)?

ANSWER: There is an obligation to add on to Shabbos at the beginning and the end. This is referred to as Tosefes Shabbos. According to many poskim, this is a Torah obligation. Although it is not clear how much time must be added, Sefer Ohr L’Tzion (vol. II, Hadlakos Neiros) writes that Tosefes Shabbos is at least 3 minutes before sunset. He recommends stopping melacha a few minutes before this, to take into account discrepancies in the calendars due to hills and other factors. Rav Moshe Feinstein zt”l (Igros Moshe OC 2:6) writes that the reason for the custom of lighting eighteen minutes before sunset was in order to fulfill the mitzvah of Tosefes Shabbos in the optimal way. However, lighting eighteen minutes before shkia is not a universal custom. Some communities have the custom of lighting twenty minutes before sunset; others light ten minutes before sunset. The custom in Jerusalem is to light forty minutes before sunset. However, eighteen minutes is the most prevalent custom. Igros Moshe writes that only the one who lights candles accepts Shabbos at that time. Others in the family may continue doing melacha for a few more minutes. It is for this reason in many homes the wife will light candles, and the husband will then drive to shul.

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The Gerald & Karin Feldhamer OU Kosher Halacha Yomis is dedicated to the memory of Rav Yisroel Belsky, zt"l, who served as halachic consultant for OU Kosher for more than 28 years; many of the responses in Halacha Yomis are based on the rulings of Rabbi Belsky. Subscribe to the Halacha Yomis daily email here.