For many years, Zunz’s study, originally published in 1859, served as a fundamental textbook for research on the history of prayer .This contemporary Hebrew translation includes research updates, many clarifications, and detailed indexes; among them an index of prayers, an index of prayer customs, an index of liturgical poetry, and an index of early manuscripts and printings of the prayer books mentioned in the study. In addition, the Hebrew edition includes notes and additions found on the author’s personal copy, never to have been published before.