14. On the day preceding Rosh HaShanah, it is a universally accepted
custom to fast until [at least] after the afternoon service ("Mincha") (1),
and then to eat something, so that one will not enter the holiday amidst
discomfort (2). One should spend the entire day occupied with Torah study,
mitzvos, and repentance. In particular, this applies concerning sins
committed against one's fellow man. One should ask their forgiveness at
this time (on Erev Rosh Hashana), rather than wait until the day before Yom
(1) If one feels even slightly ill, one should not fast (Oruch HaShulchan
(2) The Midrash states: "On Erev Rosh Hashana, the leaders of the
generation ("gedolei ha'dor") fast, and Hashem forgives ("mevater") one
third of [the nation's] sins. From Rosh Hashana to Yom Kippur, individuals
fast, and He forgives another third; then on Yom Kippur, everybody fasts,
and Hashem says to the nation of Israel: 'what has happened in the past, is
in the past; from now on, there will be a new accounting." (Ibid. 581:8).
(3) For sin's committed against one's fellow man, G-d will not fully
forgive the perpetrator until the victim himself has forgiven him.
Therefore, one must do one's best to obtain forgiveness from people one has
hurt in some way. If after doing everything possible to obtain the victim's
forgiveness, he still doesn't forgive, then the victim has sinned by not
forgiving (See Rambam, Laws of Repentance 2:9-11).