"You shall have a day of complete rest... from evening to evening." (Vayikra 23:32)
One may not do any work on Yom Kippur, as on Shabbos, so that we focus
fully on taking advantage of the unique opportunity to ask Hashem for
forgiveness for all our sins (Sefer HaChinuch, mitzvah 317).
This day is so unique that the evil inclination has no power on it. The
Talmud (Yoma 20a) teaches that the word hasatan in
gematria equals 364 because on one day a year the Satan's power is
limited. Thus, we utilize the day to gain forgiveness for the sins of the
On this day, we focus only on doing teshuva and coming closer to
Hashem(Sefer HaChinuch, mitzvah 317).