Yizkor, the prayer for the dead, is always recited on the last days of Yom Tov. Because Rosh Hashanah and Yom Kippur are, in a sense, considered one festival, Yizkor is said on Yom Kippur but not on Rosh Hashanah. By reciting Yizkor we pray for the atonement of those who can no longer acquit themselves.
As the Ne’ilah curtain falls and we descend from the seventh heaven where, we are told, God and the angels reside, we declare seven times, “The Lord, He is The God.” And on returning from our brief visit to heaven, we recite the prayer uttered by those who leave this world forever, “Shema Yisrael, Hashem Elokeinu, Hashem Echad.”
Raphael Grunfeld’s book, “Ner Eyal on Seder Moed” (distributed by Mesorah) is available at OU.org and your local Jewish bookstore. He can be contacted at firstname.lastname@example.org.