Yizkor

Hazkarat Neshamot, commonly known by its opening word Yizkor, is an Ashkenazi Jewish memorial prayer service for the dead. It is an important occasion for many Jews, even those who do not attend synagogue regularly. In most Ashkenazi communities, it is held after the Torah reading four times a year: on Yom Kippur, on the final day of Passover, on the second day of Shavuot, and on Shemini Atzeret.
Following the wording of the Jewish memorial prayer Yizkor, which is traditionally recited for an individual who has died, special versions were composed for collective commemoration.

At memorial ceremonies for Israel's fallen soldiers, particularly those held on Memorial Day for the Fallen of Israel's Wars, a special version of Yizkor is recited. The special wording of Yizkor for the fallen was first written by Berl Katznelson after the Battle of Tel Hai in 1920. During the War of Independence, a text in this spirit was composed in memory of those who fell in that war, and it was later amended to refer to all who fell in Israel's wars.
The Yizkor prayer is recited on Holocaust Remembrance Day, in memory of the victims of the Holocaust.

In Sephardic custom there is no Yizkor prayer, but the hashkavot serve a similar role in the service.

The prayer

''Yizkor text''

The version of the prayer for a person whose father has died is as follows:
May God remember the soul of my father, my teacher,
who has gone to his eternal rest, for I pledge charity on his behalf.
In reward for this, may his soul be bound in the bond of life
together with the souls of Abraham, Isaac, and Jacob; Sarah, Rebecca, Rachel, and Leah;
and together with the rest of the righteous men and women who are in the Garden of Eden.
And let us say, Amen.
In the communities of Italy, it is customary to recite Yizkor in the following version:

May God remember for good the soul of all those of His people Israel who have passed away, together with the souls of our forefathers Abraham, Isaac, and Jacob, who left a remembrance of their souls in sanctity. May they rest upon their beds in the Garden of Eden, and let us say, Amen.

Origin

The earliest source of Yizkor is the Midrash Tanchuma, which mentions the custom of remembering the deceased and pledging charity on their behalf on Yom Kippur. According to the Sifre, reciting Yizkor on Yom Kippur achieves atonement for those who have died. The service was popularized amid the persecution of Jews during the Crusades.

Customs

It is customary for those with both parents alive to leave the main sanctuary during the Yizkor service, out of respect or superstition. It is usually not attended within the first year of mourning, until the first yahrzeit/meldado has passed. The Yizkor prayers are intended to be recited in a synagogue with a minyan; if one is unable to be with a minyan, one can recite it without one. Still, this practice is a custom and historically not regarded to be obligatory.
In some congregations, Yizkor begins with responsive verses and may also include Psalm 91. In addition to personal Yizkor prayers, there are also often collective prayers for martyrs and for victims of the Holocaust, and an appeal for charity. The service concludes with the prayer El male raḥamim.
Jewish communities wrote Yizkor books to commemorate atrocities during the Holocaust. Yahrzeit candles are commonly lit on the days when Yizkor is recited.