Wikipedia
The Didache (; ), or The Teaching of the Twelve Apostles, is a brief anonymous early Christian treatise, dated by most modern scholars to the first century. The first line of this treatise is "Teaching of the Lord to the Gentiles (or Nations) by the Twelve Apostles".
The text, parts of which constitute the oldest extant written catechism, has three main sections dealing with Christian ethics, rituals such as baptism and Eucharist, and Church organization. The opening chapters describe the virtuous Way of Life and the wicked Way of Death. The Lord's Prayer is included in full. Baptism is by immersion, or by affusion if immersion is not practical. Fasting is ordered for Wednesdays and Fridays. Two primitive Eucharistic prayers are given. Church organization seems to be underdeveloped. Itinerant apostles and prophets are important, serving as "chief priests" and possibly celebrating the Eucharist. Meanwhile, local bishops and deacons also have authority and seem to be taking the place of the itinerant ministry. The Didache is considered the first example of the genre of the Church Orders. More than any other Christian scripture, the Didache reveals how Jewish Christians saw themselves and adapted their practice for gentile Christians. The Didache is similar in several ways to the Gospel of Matthew, perhaps because both texts originated in similar communities. The opening chapters are likely derived from an earlier Jewish source, and they also appear in other early Christian texts.
The Didache is considered part of the category of second-generation Christian writings known as the Apostolic Fathers. The work was considered by some Church Fathers as part of the New Testament, while being rejected as spurious or non-canonical by others, and eventually was not accepted into the New Testament canon. The Ethiopian Orthodox Church "broader canon" includes the Didascalia, a work which draws on the Didache.
Lost for centuries, a Greek manuscript of the Didache was rediscovered in 1873 by Philotheos Bryennios, Metropolitan of Nicomedia in the Codex Hierosolymitanus. A Latin version of the first five chapters was discovered in 1900 by J. Schlecht.