"...In the seventh month, on the tenth day of the month, you shall afflict your souls, and you shall not do any work ... For on that day he shall provide atonement for you to cleanse you from all your sins before the L-RD." -Leviticus 16:29-30
The Jewish Day of Atonement, Yom Kippur is the holiest day of the Jewish year.
It begins at sundown today and ends at sundown tomorrow.
Jews who observe this high holiday, fast during that time.
There are other aspects of this high holiday season between Rosh Hashanah and Yom Kippur, such as seeking forgiveness from anyone you have done wrong to - giving to charity - and doing some soul searching to see where you can improve how you conduct your life and relationships with others.
You can find out more about observances and such here.
Kol Nidre is the traditional prayer recited on the eve of Yom Kippur. The prayer is sung in synagogue by the cantor and sometimes accompanied by a choir. Here it is sung by Mordechai Ben David on the 1992 Chabad "To Life" Telethon. He is accompanied by pianist Yaron Gershovsky.
and the Kol Nidre prayer says: "All personal vows we are likely to make, all personal oaths and pledges we are likely to take between this Yom Kippur and the next Yom Kippur, we publicly renounce. Let them all be relinquished and abandoned, null and void, neither firm nor established. Let our personal vows, pledges and oaths be considered neither vows nor pledges nor oaths."
These vows and oaths are only the ones we make with God. Personal contracts and promises that we make with other people are not included. The leader and the congregation then say together three times "May all the people of Israel be forgiven, including all the strangers who live in their midst, for all the people are in fault."
In the service the Torah scrolls are then replaced, and the customary evening service begins.
What it means is that any and all rash vows made to God in the past year, and that for whatever reason were not fulfilled, could have created painful religious and ethical difficulties for those who had made them. There is an earnest desire for dispensation from them in order to wipe clean the slate for the new year. Thus came this rite of absolution from a vow ('hattarat nedarim'). The rite is performed as if in a court of Jewish law (Bet Din) which might be performed only by a scholar, or an expert on the one hand, or by a board of three Jewish laymen on the other. This rite declares that those who recite Kol Nidre, and are seeking reconciliation with God, solemnly retract the vows and oaths which they have made to God during the period intervening between the previous Day of Atonement and the present one; this rite makes those vows null and void from the beginning, entreating in their stead pardon and forgiveness from God. This is in accordance with the older text of the formula as it is preserved in the Siddur of Amram Gaon.
Some of the YouTube renditions of the Kol Nidre Prayer are really quite lovely, as is the musical performances.
I wish all my Jewish readers a Happy New Year - and an easy fast on Yom Kippur. G'mar Hatima Tova! May you be inscribed in the Book of Life. (Literally: 'A Good and Significant Finishing')