One message - ichimai shosoku

...A document that writes the essentials of Nembutsu in simple language on a single sheet of paper, and vows to Shaka and Amida that it is true. It is also called "Ichi-mai no Shosoku." On January 23, 1212 (Kenryaku 2), Genchi, who had always served Honen, learned that his master was nearing the end of his life. Fearing that disagreements would arise among his disciples after his death, he pleaded for the essentials of the Jodo sect's Anjin Kigyo (peaceful starting and practicing). Honen responded by doing so himself and bestowed it on Genchi....

*Some of the terminology explanations that refer to "One Message" are listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…念仏の要義を1枚の紙に平易な文章で書き，釈迦･弥陀に偽りのないことを誓った文。〈一枚消息〉ともいう。1212年(建暦2)1月23日，つねに法然のもとで仕えてきた源智が，師の命終が近いことを知り，没後に門人たちの間で異義の生じることを恐れ，浄土宗の安心起行（あんじんきぎよう）の肝要を懇望したので，法然がこれに応じてみずからしたため源智に授与した。…

※「一枚消息」について言及している用語解説の一部を掲載しています。

出典｜株式会社平凡社世界大百科事典 第２版について | 情報