(80-120 AD) This is a Greek epistle containing twenty-one chapters, preserved complete in the 4th century Codex Sinaiticus where it appears at the end of the New Testament. It is traditionally ascribed to Barnabas who is mentioned in the Acts of the Apostles, although some ascribe it to another Apostolic Father of the same name, “Barnabas of Alexandria”, or simply attribute it to an unknown early Christian teacher.
Toward the end of the 2nd century Clement of Alexandria cites the Epistle. It is also appealed to by Origen of Alexandria. Eusebius, the first major church historian, however, recorded objection to it, and ultimately the epistle disappeared from the appendix to the New Testament, or rather the appendix disappeared with the epistle. In the West the epistle never enjoyed canonical authority (though it stands beside the Epistle of James in the Latin manuscripts). In the East, the Stichometry of Nicephorus, the list appended by the 9th century Patriarch of Jerusalem to his Chronography, lists the Epistle of Barnabas in a secondary list, of books that are antilegomena— “disputed”— along with the Revelation of John, the Revelation of Peter and the Gospel of the Hebrews. [excerpt from Wikipedia]