Yom Kippur is the holiest day of the year—the day on which we are closest to God. It is the Day of Atonement—"For on this day He will forgive you, to purify you, that you be cleansed from all your sins before God" (Leviticus 16:30).
In Biblical times, when the Temple was standing, Yom Kippur was the one day of the year when the Cohen Gadol, the High Priest entered the Holy of Holies and performed the atonement ritual on behalf of the entire community before the Ark of The Covenant. The High Priest wore white robes on Yom Kippur—today as both an act of remembrance of the Temple services, and to symbolize the purity that represents God’s cleansing, we wear white also. We also refrain from wearing leather and excessive outer adornment such as jewelry and other fine things to symbolize that neither wealth nor poverty divide us, but we are all equal before the eyes of God.
During the Days of Awe we come before God to give an account of our life, our actions, and interactions, and then place our trust in Him for another year of life. Of course, it is important to do this as individuals, but the services and activities are designed to bring us together as a community. We stand before God as one people and give an account corporately. We then recommit our lives collectively as a whole people—the people of God. On Yom Kippur God’s decree is sealed. Our sin has been removed—we start over with a clean slate. We begin the year to walk in God’s ways anew.
This year Yom Kippur falls on September 25, the Hebrew month Tishrei. In the course of Yom Kippur we hold five prayer services: Maariv, with its solemn Kol Nidrei service, on the eve of Yom Kippur; Shacharit—the morning prayer; Musaf, which includes a detailed account of the Yom Kippur Temple service; Minchah, which includes the reading of the Book of Jonah; and Neilah, the "closing of the gates" service at sunset. We say the Al Chet confession of sins eight times in the course of Yom Kippur, and recite extensively from the Book of Psalms.
The last shofar call at the close of Yom Kippur is a loud, clear tekiah g’dolah that is extended for as long as the one blowing it has breath. Psalm 27 addresses our fear at the uncertainty of life, with all its threats and dangers, and our consequent plea that God not hide His face from us and that He will neither abandon nor forsake us. Yom Kippur concludes with a proclamation of faith that all our hope and trust are in Him. “Put your hope in ADONAI, be strong, and let your heart take courage! Yes, put your hope in ADONAI!” (Psa 27:14).
For nearly twenty-six hours, from several minutes before sunset on Tishrei 9 to after nightfall on Tishrei 10, we "afflict our souls"—we abstain from food and drink, do not wash or anoint our bodies, do not wear leather footwear, and abstain from marital relations.
The day is the most solemn of the year, yet an undertone of joy suffuses it—a joy that revels in the spirituality of the day and expresses the confidence that God will accept our repentance, forgive our sins, and seal our verdict for a year of life, health and happiness. The closing Neilah service climaxes in the resounding cries of "Hear O Israel, the LORD is our God, the LORD is One" (Deu 6:4). Then joy erupts in song and dance followed by a single blast of the shofar, followed by the proclamation, "Next year in Jerusalem." We then partake of a festive after-fast meal, making the evening after Yom Kippur a Yom Tov (festival) in its own right.