Philip Schaff 
The Didache : TEACHING of the TWELVE APOSTLES [EPUB ebook] 
Also Includes The Epistle of Barnabas

The Didache was possibly written around 65 – 80 A.D. and is supposed to be what the twelve apostles taught to the Gentiles concerning life and death, church order, fasting, baptism, prayer, etc. There is debate as to its authenticity.
In the Babel of conflicting opinions, it is best to notice first the obvious internal phenomena. The first part of the Teaching (now distinguished as chaps. i.-vi.) sets forth the duty of the Christian; in chaps. vii.-x., xiv., we find a directory for worship; chaps. xi.-xiii., xv., give advice respecting church officers, extraordinary and local, and the reception of Christians; the closing chapter (xvi.) enjoins watchfulness in view of the coming of Christ, which is then described.
The most striking internal phenomena are, however, the correspondences of this document with early Christian writings, from a.d. 125 to the fourth century. With the so-called Epistle to Barnabas, chaps. xviii.-xx., the resemblances are so marked as to demand a critical theory which can account for them.