"...when they take off her robes and cover up her statue. Because of this, the Athenians especially consider this day to be the worst of unlucky days to do anything. The goddess, then, did not appear to receive Alkibiades with welcome or favor, but to hide herself and to drive him away from her."
https://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.01.0181%3Achapter%3D34