The Teaching of the Twelve Apostles, commonly known as Didachē, which means “Teaching,” is a brief early Christian treatise, dated by most scholars to the late first or early 2nd century A.D. The text, parts of which may have constituted the first written catechism, has three main sections dealing with Christian lessons, rituals such as baptism and Eucharist, and Church organization. It is considered the first treatise of the genre of the Church Orders.
The Didache was considered by some of the Church Fathers as part of the New Testament but rejected as non-canonical by others and was eventually left out of the New Testament. The Ethiopian Orthodox Church “broader canon” includes the Didascalia which was based on the Didache.
Lost for several centuries, the Didache was rediscovered in 1873 by Philotheos Bryennios, Metropolitan of Nicomedia in the Codex Hierosolymitanus. An English translation was first published in 1883. It is considered part of the collection of Apostolic Fathers.