In the Tenrikyo religion, the Osashizu ("Divine Directions") is a written record of oral revelations given by Izo Iburi. It is one of the three scriptures (sangenten ???) of Tenrikyo, along with the Ofudesaki ("The Tip of the Writing Brush") and the Mikagura-uta ("The Songs for the Service"). The full scripture is published in seven volumes (plus an index in three volumes) and contains around 20,000 "divine directions" delivered between January 4, 1887 and June 9, 1907.
O is an honorific prefix, while sashizu may refer to "instruction(s)" or "direction(s)."
In Tenrikyo parlance, the term Osashizu technically has two senses, a broader and a narrower one. In its broader sense, the Osashizu includes all of the oral revelations given by Miki Nakayama (who followers refer to as Oyasama or the "Foundress"), and Izo Iburi (who followers refer to as the Honseki, or the "Main Seat"). In its narrower sense, the Osashizu simply denotes the transcriptions of those revelations. 
In the first few years after 1887, the main scribe of the Osashizu was probably Shobei Masuno. The directions from 1887-1888, the earliest records of the Osashizu, are difficult to understand, possibly because the scribe was simply unable to write down all of the words that were said. Eventually a system developed (it is unknown exactly when) where Iburi's directions would be transcribed by three ministers who were on duty at Iburi's residence. While a direction was being delivered, each of them would write a transcription of the direction on rough rice paper with a writing brush. After the direction was completed, the ministers would read over what they had transcribed and locate any mistakes, misheard words, or missing phrases and prepare a clean copy. Masajin Iburi (Izo Iburi's son) was the main scribe of the Osashizu in the fourth decade of the Meiji era (1897-1906) and by his time, the transcriptions were consistent in intelligibility.
When a inquirer wanted to request a divine revelation from Izo Iburi, the procedure was to approach an intermediary, who would relay the inquiry to the Shinbashira (the leader of Tenrikyo, who at the time was Shinnosuke Nakayama), who in turn would relay it to Iburi. The directions in response to the inquiry would be written down while they were being delivered, and the transcriptions would be given to the inquirers.
The original edition of the Osashizu was published in thirty-three volumes between 1927 and 1931. In 1931, the three scriptures, the Ofudesaki, the Mikagura-uta, and the Osashizu, had become available to all followers.Then the Osashizu was recompiled and published as a set of eight volumes in 1936-1937, commemorating important anniversaries for Miki Nakayama and the founding of Tenrikyo.
The current edition of the Osashizu (in Japanese) was published between October 1963 and January 1966. The preparation of the current edition involved, among other efforts, revising punctuation, which originally made use of only commas and no periods, applying Chinese characters wherever possible since the original transcriptions were written almost entirely in the Japanese syllabary; and incorporating newly collected and authenticated transcriptions.
As of 2017, Tenrikyo Church Headquarters has yet to publish an English translation of the entire Osashizu. Selected translations of the Osashizu have been published under the titles, Selections from the Osashizu (1976, revised 1990) and An Anthology of Osashizu Translations (2007).
The directions in the Osashizu have been classified into two types, "Timely Talks," which were unprompted revelations, and "Directions in Response to Inquiries," which were revelations provided in response to an inquiry. Individuals or groups would make inquiries about illness, natural disasters, personal issues, and church affairs.