The Apostolic Constitutions is a late 4th century collection, in 8 books, of independent, though closely related, treatises on Early Christian discipline, worship, and doctrine, intended to serve as a manual of guidance for the clergy, and to some extent for the laity. It purports to be the work of the Twelve Apostles, whose instructions, whether given by them as individuals or as a body, are supposed to be gathered and handed down by the compiler, Clement of Rome, the authority of whose name gave weight to more than one such piece of early Christian literature (see also Clementine literature). Where known they were held generally in high esteem and served as the basis for much ecclesiastical legislation. They are today of the highest value as a historical document, revealing the moral and religious conditions and the liturgical observances of the 3rd and 4th centuries. They are part of the Ante-Nicene Fathers collection.
The first 6 books are based on the Didascalia Apostolorum , a lost treatise of the third century, of Greek origin, which is known through Syriac versions. The 7th book is based on the Didache. The 8th book is a mixed compilation. The introductory chapters (i-ii) have for their foundation a treatise entitled "Teaching of the Holy Apostles concerning Gifts", possibly a lost work of Hippolytus. The 3rd chapter appears to be a work of the compiler. Chapters (iv-xlvi) present difficulties the varied solution of which divides scholars as to its sources. The last chapter (xlvii) contains the Canons of the Apostles said to be from an apostolic Council at Antioch and later approved by the Orthodox Quinisext Council in 692 but rejected by Pope Constantine. Canon #85  is this list of canonical books: a 46-book Old Testament canon which essentially corresponds to that of the Septuagint, 26 books of what is now the New Testament (excludes Revelation), the Didache, two Epistles of Clement, and the Apostolic Constitutions themselves, also here attributed to Clement, at least as compiler.
The Apostolic Constitutions were rejected as canonical by the Decretum Gelasianum and the Sixty Books canon and the Quinisext Council in 692 because they were said to contain heretical interpolations, however these canons were later accepted and confirmed by Pope Hadrian I . They were accepted as canonical by John of Damascus and the Ethiopian Orthodox 81 book canon.
From John William Donaldson's introduction: "There has always existed a great diversity of opinion as to the author and date of the Apostolical Constitutions. Earlier writers were inclined to assign them to the apostolic age, and to Clement; but much discussion ensued, and the questions to which they give rise are still unsettled. The most peculiar opinion in regard to them is that of William Whiston, who devoted the third volume of his Primitive Christianity Revived to prove that "they are the most sacred of the canonical books of the New Testament; "for "these sacred Christian laws or constitutions were delivered at Jerusalem, and in Mount Sion, by our Saviour to the eleven apostles there assembled after His resurrection.""
- Catholic Encyclopedia: Apostolic Constitutions source of some of the above
- Apostolic Constitutions
- Jewish Encyclopedia: Didascalia
- Apostolical Constitutions in the 1911 Encyclopædia Britannica
- Schaff-Herzog Encyclopedia of Religious Knowledge: Apostolic Constitutions and Canonsru:Апостольские постановления