"Many people use the phrase "Never again!" when discussing the Holocaust. For Elie Wiesel, it's more than a phrase. It's his life's mission."
Then Noah built an altar to the LORD and, taking some of all the clean animals and clean birds, he sacrificed burnt offerings on it. The LORD smelled the pleasing aroma and said in his heart: "Never again will I curse the ground because of man, even though every inclination of his heart is evil from childhood. And never again will I destroy all living creatures, as I have done. — Genesis 8:20-21 (NIV)
Salomon Isaacides, commonly known by the acronym of Rashi, was the hugely influential 11th century (AD) French rabbi, whose commentary on the Babylonian Tamud has been included in every print of the Talmud for almost 500 years. He also wrote a commentary on the Tanakh (Jewish Bible), in which he stated of the Jewish god using the phrase "never again" twice in Genesis 8:21:
He repeated the words to denote an oath
So the much used phrase "never again", has religious significance to Jews, it was an oath made to them by their god. But even more revealing was something written by Menachem Mendel Schneerson, known as the Rebbe, the leader of the hasidic Chabad Lubavitch cult, and hailed by his powerful followers as the long awaited Jewish messiah (although he died in 1994, they are expecting him to come back—somehow). Schneerson wrote a commentary on Rashi's commentary of the Torah (included in the Tanakh), he stated of Rashi insight above:
This implies that a Divine oath occurs as a direct result of man offering a sacrifice, since God swore the oath only when He "smelled the pleasant aroma."
So according to the Rebbe, before the the Jewish god will make a Divine oath, he requires a sacrifice, a burnt offering, a holocaust.
Miller, Chaim. Chumash: The Book of Genesis. The Gutnick Edition New York: Kol Menachem. 2008. p.134