an early Christian work written in Greek by one of the so-called Apostolic Fathers, Greek Christian writers of the late 1st and early 2nd centuries. Ascribed by tradition to St. Barnabas (Barnabas, Saint), the Apostle, the writing dates possibly from as late as AD 130 and was the work of an unknown author who refers to himself in the letter as a teacher.

The Letter of Barnabas was essentially a treatise on the use of the Old Testament by Christians. Very anti-Jewish, the author believed that the Old Testament could not be understood by Jews and that its significance could be understood only by those who read it and searched for types, or prefigurations, of Jesus. At the end of the letter the author discusses the ways of light and darkness—i.e., the ways of good and of evil.

Evidently regarded as scriptural in Egypt, the Letter of Barnabas was included in the Codex Sinaiticus, a 4th-century Greek manuscript of the Bible, and it was also quoted by the presbyter Clement of Alexandria (d. c. 215). It was less highly regarded elsewhere, however, and few Christians continued to read it.