Candle-Lighting Time: 18, 25, or 40 Minutes?

If Shabbos begins at shkiah, why do we light the candles earlier?

Shabbos begins at shkiah (sunset). The time between shkiah and nightfall, bein hashmashos, is a doubtful period that may already be night (see calculation in issue 601). Melacha is then forbidden mide’oraisa, and one who did melacha at that time would have to bring an asham talui, the korban brought for a doubtful sin.¹

In addition, there is a mitzvah to add time from the weekday onto Shabbos, tosefes Shabbos, by stopping melacha a little before shkiah, as long as the time added is certainly still day.² Shabbos may be accepted as early as plag hamincha, one and a quarter halachic hours before sunset, but not earlier (see issue 314).³ In the summer, when Shabbos comes in late, young girls may light beginning from plag and accept Shabbos then, even if their mother lights later.⁴

For a woman, lighting the candles is her acceptance of Shabbos. If she stipulates otherwise, she or her husband must still accept Shabbos soon after (see issue 704). Her lighting time is therefore, in effect, the start of her Shabbos, and it must leave room for tosefes Shabbos before sunset.

Why eighteen minutes? Rava told his attendant, “You, who are not experts in the exact measure of the Sages, light the lamp while the sun is still on the treetops.”⁵ The Alter Rebbe likewise writes that one must be “very, very careful” to light before sunset, noting that in winter many women stumble and light late,⁶ and that a person should accept Shabbos well before sunset.⁷ The Rebbe asked to publicize that candle-lighting is at least 18 minutes before sunset.⁸ The Mishnah Berurah calls one who stops melacha 20-30 minutes before sunset praiseworthy, since he satisfies all the Rishonim.⁹

The published time is a margin, not the deadline. One who is running late may still light, as long as it is before sunset. After sunset, however, lighting is an issur de’oraisa, and it is no mitzvah at all but the opposite ch”v (on what to do then, see issue 899).¹⁰

Customs vary from place to place. Many communities light 18-20 minutes before shkiah.¹¹ In Eretz Yisroel, many light 22-30 minutes before shkiah,¹² while in Yerushalayim the custom is 40 minutes.¹³ The widespread custom, and the Chabad custom, is 18 minutes. However, where the local community lights at an earlier time, one should follow it. ¹⁴

In the Rebbe’s home, the candles were lit twenty-five minutes before shkiah, and the Rebbe remarked that this was the custom in Lubavitch.¹⁵ The eighteen minutes in the Rebbe’s letter is apparently the standard calendar time (absent another local custom), and even that is a minimum.

See Sources (open PDF)