When the Prophets Cried is a piece of Bajoran literature written by Vedek Synta Kayanil that told the stories of the discovery of the first seven Orbs of the Prophets. Some of the chapters were called The Third Tear, Home in the Firmament, Bajor Rises and Prophecy. By the 24th century, Synta's book had become a canonical part of the Bajoran religion.
Kira Nerys was given a copy the book by Klyta, whose ancestors had passed it down from generation to generation, after Klyta was killed by the Cardassians during the Occupation of Bajor. Kira would keep the book with her at all times when he was part of the Bajoran Resistance and later when she joined the Bajoran Militia and was posted to Deep Space 9. She would often read it when she needed guidance, solace, inspiration, or enlightenment. Captain Benjamin Sisko had read the tome several times before 2372 and planned to quote from it when trying to get the Ferengi to give the Orb of Wisdom to the Bajorans. (DS9 novel: The 34th Rule)
As part of her Attainder in 2376, Kira was forbidden from reading any books of the Bajoran religious canon, including When the Prophets Cried. Kira decided to read the book anyway. (DS9 - Mission Gamma novel: Twilight)