Alter Rebbe’s Sof Zman Krias Shema

Ask the Rov: Why are there two zmanim for the latest Shema time on the zmanim calendars?

By Rabbi Chaim Hillel Raskin – Rov of Anash in Petach Tikvah

The mishna quotes several opinions regarding the latest time in the morning to fulfill the mitzvah of shema. Halacha rules that one has until the end of the third hour of the day, since children of royalty are still waking up at that time.¹

The hours referred to are shaos zmaniyos (“seasonal hours”), which are each a twelfth of the daytime on that particular day. Halachic hours are longer than sixty minutes in the summer and shorter than sixty minutes in the winter, and the difference grows the further north or south the location is. Some poskim measure with 60-minute hours (i.e., end of ⁹ hours from halachic midnight), and although the halacha isn’t so, one who missed the official zman should at least try before this zman, which is sometimes a later option in the summer.²

Some achronim — notably, the Magen Avrohom and the Alter Rebbe in his Shulchan Aruch — consider daytime hours to be from alos hashachar (dawn) to tzeis hakochavim (nightfall).³Shema may be recited b’dieved from alos hashachar, as some people already begin waking up at that time, so this view holds that the three seasonal hours begin then.⁴

However, the Alter Rebbe in his siddur and others — like the Gra — hold that the day begins at netz hachama (sunrise) and ends at shkiah (sunset). (Within the Alter Rebbe’s view, some understand the calculation to be based on the “true” shkiah, which is slightly later, and some also mirror this adjustment for the “true” sunrise, which is slightly earlier.) Thus, the seasonal hours are shorter, but are counted from sunrise, resulting in a later zman.

Some explain that the counting of daytime from dawn followed the original custom to accept Rabbeinu Tam’s view on shkiah, according to which bein hashmashos only begins around an hour after the visible sunset, leaving official “daytime” after sunset. But once the custom accepted the Geonim’s view, that bein hashmashos starts at the visible sunset, the daytime in the morning also only starts from sunrise and not dawn.⁵

Thus, those who are makpid on the morning krias shema before the earlier zman ought to be makpid to recite the evening krias shema after Rabbeinu Tam’s shkiah, as the two are interdependent.⁶

Notably, the Alter Rebbe writes in the Siddur that one should not wait until the last minute, especially because clocks may not be precise, but rather fulfill the mitzvah with ample time to spare (finishing shema 45 minutes early).

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From The Weekly Farbrengen by Merkaz Anash