10. On Friday, from nine seasonal hours (1) into the day and onwards,(2)
it is a mitzvah (obligation) to refrain from eating a regular meal, (3)
even if one is accustomed to eat such a meal on other weekdays.
Furthermore, a meal that one is unaccustomed to eat on other weekdays, may
not be eaten throughout the entire day, even during the morning. This
restriction applies even to a meal associated with a mitzvah, if it could
be held on another day. However, a meal associated with a mitzvah that has
a set time, such as circumcision, the redemption of a firstborn, and the
like, (4) may be held on Friday; nevertheless, one should hold it in the
early morning, and not make it extravagant. It goes without saying that a
person should not overeat at the meal, so that he will be able to eat the
Sabbath meal on Friday night with a hearty appetite.
(1) These are not the standard 60 minute hours. Seasonal hours ("Shaos
Zemanios") are calculated by dividing the length of the day (some say from
sunrise to sunset; others, from daybreak to the appearance of 3 stars) into
12 equal parts; each part is referred to as one "hour." For example, if
daylight lasts 18 regular hours, each seasonal hour would be 90 minutes long.
(2) On shorter Fridays, one should refrain from eating a meal even earlier,
if it will spoil one's appetite (Mishna Berura).
(3) To show the importance of this Mitzvah, the Talmud (Tractate Gittin
38b) relates the following: "There were two families living in Jerusalem,
one would regularly hold their meal on the Sabbath [while the Rabbi was
giving his sermon in the study hall], the other would regularly have a meal
on Friday (after the 9th hour); both families were destroyed."
(4) For example, a "Siyum," a meal celebrating the completion of a tractate
of Talmud (Biur Halacha 249:2).
