In the novel Night by Elie Wiesel, "Men to the left! Women to the right," is found on the first page of Chapter 3, page 29. As they disembark the train that has brought them to the gates of hell, they are met by a club weilding SS officer. These are the first words that Elie and his family hear when arriving at the dreaded Birkenau concentration camp.
At this point, Elie and his father are mirror images of his mother and his sister Tzipora. Each child holding the protective hand of a parent who can no longer offer them protection, and the significance of this moment is that it is the last time Elie ever saw his mother and sister.