The ancient church orders form a genre of early Christian literature, ranging from 1st to 5th century, which has the purpose of offering authoritative "apostolic" prescriptions on matters of moral conduct, liturgy and Church organization. These texts are extremely important in the study of early liturgy and served as the basis for much ancient ecclesiastical legislation.
A characteristic of this genre is their pseudepigraphic form. Many of them profess to have been handed down by the Twelve Apostles, in some case purported to have been gathered by Clement of Rome or by Hippolytus of Rome. In the earliest of them, the Didache, extends to the title: The teaching of the Lord to the Gentiles by the Twelve Apostles. The later Testamentum Domini declares itself to be the legacy left by Jesus Christ himself to his Apostles before the Ascension, and to give his own words and commands as to the government of the Church. Apart from the Apostolic Constitutions, which was printed before 1563, all other texts have been discovered and published in the 19th or early 20th century.
Church orders were mutually interrelated documents and often circulated in collections. It is easy to point out many direct literal relationships among sections of them. Different scholars since the early 20th century have suggested extremely different historical orders of interrelation. Nowadays the usually accepted family tree contains different roots, and can be so summarized according to Bradshaw:
There are other minor texts belonging to the genre of the ancient church orders: the Coptic Canons of Basil (an Egyptian 4th-century text based mainly on the Canons of Hippolytus) and the Western Statuta Eccesiae Antiqua (about 490 AD, probably composed by Gennadius of Massilia and based on both Apostolic Tradition and Apostolic Constitutions).
Usually the church orders were transmitted in collections with the same order of materials, even if sometimes free rendered and mixed with additional material. The more ancient collection is formed by Didascalia - Didache - Apostolic Tradition. Later the Apostolic Church-Ordinance took the place of the Didache in the second position and in even later manuscripts the Testamentum Domini took the place of the Didascalia in the first position and the book 8 of the Apostolic Constitutions took the place of the Apostolic Tradition in the last position, thus we find Testamentum Domini - Apostolic Church-Ordinance - book 8 of the Apostolic Constitutions.
The main collections of church orders are the following:
To indicate the way of development of the ancient church orders the term "living literature" has been proposed by Bruce M. Metzger and Paul F. Bradshaw (and others) in order to note that these texts, of which only a part survived, were updated and amended generation after generation, mixing ancient parts with materials from the contemporary uses and tradition of the copyists and removing what was no more in line with the current understanding. Moreover, it is probable also that in many cases the copyists were not describing their current or more ancient uses, but what they considered to be the best practice, thus for example describing liturgies never performed. This kind of literature allows the scholars, after a process of evaluation, to look at the liturgies of the 3rd and 4th century, but it makes difficult to use these texts to describe more ancient liturgies.
It is possible to outline also some development patterns for the content of this literature: the more ancient texts, such as Didache, are mainly concerned about moral conduct, giving very little room to liturgy and to Church organization. Later on the interest on moral issues waned and liturgy became prominent. In the last documents, the focus moved mainly on the Church organization and to the canon law. Starting since the 5th century, the ancient church orders ceased to be regarded as authoritative, in spite of their higher and higher claimed level of pseudepigraphy, and were substituted by the canons of councils and synods and by sacramentaries of famous bishops.