Article: Why do we say Vidui so many times?
Vidui (confession) is a part of the process of teshuvah (returning to Hashem), accomplished through verbalizing our sins. The vidui procedure was an essential aspect of bringing korbanos (sacrifices) in the Beis Hamikdash (Holy Temple). We recite vidui whenever we atone for wrongdoing, and specifically, ten times during the course of the tefillos (prayers) of Yom Kippur (the Day of Atonement). By reciting the vidui, we fulfill a mitzvah min haTorah (Biblical commandment, although teshuvah itself is not counted as one of the six hundred thirteen).
The ten times we recite the vidui on Yom Kippur (each prayer encompasses all the numerous declarations of al cheit—“for the sin of…”—admissions) corresponds to the ten instances in the original Yom Kippur service in the Beis Hamikdash when the Kohen Gadol (High Priest) uttered the Shem haMeforash (Hashem’s ineffable name).
The vidui should be recited me’umad (while standing)—both when it is said as part of the silent individual tefillos and when it is repeated during chazaras hashatz (the prayer leader’s repetition). While standing and reciting the vidui, we submit ourselves to Hashem completely by bending our heads forward slightly, striking our chests for each of the admissions—when we say “al cheit shechatanu”. While standing, the davener may not lean on a prop to the extent that if it were removed, they would fall.
There is discussion among the Rishonim (early halachic authorities) when is the proper time for saying the evening vidui—before or after nightfall on the eve of Yom Kippur. Although the consensus is that the mitzvah is fulfilled by reciting it on the fast itself, it should also be recited just before sunset on Erev Yom Kippur (though it does not appear in that place in many standard Machzorim—High Holiday prayer books). This recitation is in accordance with the opinion of the Ramban: the purpose of saying vidui at that time is to atone by saying al cheit—and when forgiven with no further opportunity or time to transgress—enter into the holy day of Yom Kippur free of sin.
Sources:
From Halacha2Go Archives
#723
