The Epistle of Barnabas is sometimes found in the canonical listing of New Testament books. Origen even quotes it as Scripture in his Commentary on Romans (1.18). Subsequent history demonstrates that it ultimately was not considered as part of the New Testament Scriptures. It was probably written some time after the destruction of Jerusalem but before Hadrian's rebuilding of the city (ca. 132-135 A.D.). This makes it highly unlikely that the real Barnabas, who was a companion of Paul's, was its author. It most likely originated in Alexandria where Philo, an Alexandrian Jew and contemporary of Paul, lived. Philo was known for his allegorical interpretations of the Jewish Scriptures, and Alexandria became a center for such interpretation. Clement of Alexandria (ca. 160-215 A.D.) is the first to ascribe the epistle to Barnabas and uses it quite extensively to support his own allegorical interpretation.  Allegory is an interpretive approach to Scripture that tries to find a hidden spiritual meaning when the literal meaning seems to provide little spiritual enlightenment.  

The Epistle of Barnabas is especially significant because it is one of earliest attempts on the part of the Christian Community, outside of the New Testament, to reconcile itself with the Jewish Scriptures. This epistle is an exploration of the relationship between Christianity and Judaism at a time when the antagonism between the two is obviously still quite high. Its solution is to read everything in the Old Testament in light of Jesus' life and teachings. Therefore only the Christian understands the true meaning of the Scriptures, according to Epistle of Barnabas 10.12.  The sacrifice of Isaac, the goat that was led into the desert, Moses with his arms extended in the shape of the cross, and the serpent raised up in the desert are all figures, or "types" of Jesus Christ and his work of salvation.  While all of these things really happened, the deeper significance is what they teach us about Jesus and how they pointed ahead to him. In addition, they are an affirmation of the pre-existence of Christ and his role in creation [5.5].  

All of this occurs in the first part of the epistle in chapters 1-17. The last four chapters contain the teaching of the two ways, or two powers. (We also find these at the beginning of the Didache, which may point to a common source for this teaching). There is the Way of Light and the Way of Darkness. The two ways are incompatible with each other and there can be no association between them. One is guarded by light-giving angels, the other by the angels of Satan. Those who follow the Way of Light will refrain from any sexual immorality, pride, lying, hatred or grudges. There is a specific prohibition against abortion (in Greek, phthora) and infanticide (19.5), and a strong admonition to discipline one's children. It also teaches respect for slaves and counsels those of the light to have a generous spirit. The Way of Darkness leads to eternal death and punishment because it is filled with all the things that destroy souls: "idolatry, audacity, exaltation of power, hypocrisy, duplicity, adultery, murder, robbery, arrogance, transgression, deceit, malice stubbornness, sorcery, magic art, greed, lack of fear of God" (20.1). The Epistle leaves no doubt that this is no dualistic battle between two equal powers. The Light always overcomes the darkness (John 1:5).