Chapter 128:15
The Month of Elul
15. We should wash our clothes and cut our hair (and shave) on Erev Rosh
Hashana in honor of the festival. Hair should be cut before "Chatzos"
("midday") (1). One should also immerse in a mikveh (2).
We wear our Shabbos clothing (3) on Rosh HaShanah to show that we are
confident of G-d's grace, and that he will judge us favorably (4).
FOOTNOTES:
(1) Halachic midday, "chatzos," is calculated by totaling the number of
minutes from dawn ("alos ha'shachar") until the appearance of 3 stars
("tzeis ha'kochavim"), and then dividing it in half (some say from sunrise
to sunset).
(2) One should not immerse until at least one hour before "Chatzos" (Mishna
Berura 581:26).
(3) The Mishna Berura writes that one should tone down a little on what one
would wear on another Yom Tov, so as to remain in awe of the gravity of the
judgement that is taking place (Ibid. 581:25).
(4) Here is a quote from the Tur (O"H 581) based on the Midrash: "What
other nation is like this one, that understands the personality of its
God!...The accepted custom of one who faces judgement is to wear black, to
wrap himself in mourning, neglect his hair and fingernails - for he dreads
the unknown results of the judgement. But not Yisrael! They wear white,
wrap themselves in white, groom their hair and fingernails, eat and drink
and rejoice on Rosh Hashana, knowing that the Holy One will perform a
miracle for them...
The Maharshal comments on the above Midrash: "Then why not wear embroidered
and colorful clothing? ...That might imply that he does not fear the Day of
Judgement at all and is insensitive, but wearing white demonstrates
awareness of the day of death...