Who is attributed with saying, "Sometimes the magic works, and sometimes it doesn't."?

Little Big Man is a 1970 American western comedy-drama film directed by Arthur Penn and based on the novel Little Big Man by Thomas Berger. It is about a white male child raised by the Cheyenne nation during the 19th century. The film is largely concerned with contrasting the lives of American pioneers and Native Americans throughout the progression of the boy's life.

The movie stars Dustin Hoffman, Chief Dan George, Faye Dunaway, Martin Balsam, Jeff Corey and Richard Mulligan. It is considered a Western, with Native Americans receiving a more sympathetic treatment and the United States Cavalry depicted as villains.

Back at the Indian camp, Jack accompanies Old Lodge Skins to a nearby hill, the Indian burial ground, where the old man, dressed in full chief's regalia, has declared "It is a good day to die", and decides to end his life with dignity. He offers his spirit to the Great Spirit, and lies down at his spot at the Indian Burial Ground to wait for death. Instead, it begins to rain. Old Lodge Skins is revealed to still be alive, and says, "Sometimes the magic works, and sometimes it doesn't". They return to his tepee to have dinner.