For Barnabas and his Gentile Christian followers, the covenant between God and the Jews was a sham; it was never ratified. When, bringing down the Law from Sinai, Moses saw that the Jews were engaged in the worship of the golden calf, he smashed into pieces the two stone tablets inscribed by God's hand, and thus rendered the Jewish covenant null and void. It had to be replaced by the covenant sealed by the redemptive blood of the "beloved Jesus" in the heart of the Christians (Barn. 4. 6-8; 14. 1-7).
Barnabas's portrait of Jesus is considerably more advanced than the Didache's "Servant" of God. He calls Jesus "the Son" or "the Son of God" no less than a dozen times. This "Son of God" had existed since all eternity and was active before the creation of the world. It was to this pre-existent Jesus that at the time of "the foundation of the world" God addressed the words, "Let us make man according to our image and likeness" (Barn. 5.5; 6.12). The quasi-divine character of Jesus is implied when Barnabas explains that the Son of God took on a human body because without such a disguise no one would have been able to look at him and stay alive (Barn. 5. 9-10).
The ultimate purpose of the descent of "the Lord of the entire world" among men was to enable himself to suffer "in order to destroy death and show that there is resurrection" (Barn. 5. 5-6). We are in, and perhaps slightly beyond, the Pauline-Johannine vision of Christ and his work of salvation.
The type of outlook represented by the Didache has no place in the religious vision of Barnabas. The parting of the ways between Jewish and Gentile Christianity is manifest already at this stage and the Epistle of Barnabas marks the start of the future doctrinal evolution of the church on exclusively Gentile lines. Half a century after Barnabas, for the bishop of Sardis, Melito, the Jews are judged guilty of deicide: "God has been murdered...by the right hand of Israel" (Paschal Homily 96). Jewish Christianity makes no sense any longer.And it fell, as Chesterton said of Carthage, like nothing has fallen since... well, perhaps the image is inapt here. If it is, though, we might ask just why.
The Didache is the last flowering of Judaeo-Christianity. In the second century, and especially after the suppression of the second revolt of the Jews by Hadrian in 135 CE, its decline began.