Hartin, Patrick J. "Chapter Thirteen: Ethics in the letter of James, the Gospel of Matthew, and the Didache: Their Place in Early Christian literature." in Van de Sandt, Huub & Zangenberg, Jürgen K. (editors). Matthew, James, and Didache: Three Related Documents in their Jewish and Christian Settings." Atlanta, GA: Society of Biblical Literature, 2008, 289-314.
Hartin considers the relationship of the ethical world of Israel and of Christianity, as addressed in James, the Didache, and Matthew, taking them in that order, which he thinks is the order of composition (Hartin 2008, 289). The ethical world is important as it largely provides a means to identify a particular group (Hartin 2008, 290).
James, addressing people of Israel who are dispersed, roots their identity in belonging to Israel (Hartin 2008, 291). There is an eschatological hope of restoration. They are pictured as rooted in the Torah, God's law (Hartin 2008, 292). The Law creates the identity of the people by describing how God has dealt with His people (Hartin 2008, 292). This socializes them in a particular way.
Matthew's Gospel is also rooted in the historical people of Israel (Hartin 2008, 293). Jesus' ministry and that of his disciples primarily focuses on Israel, not the Gentiles. Jesus specifically denies coming to do away with Torah, but affirms it and fulfills it (Hartin 2008, 294).
Hartin further finds the Didache to be rooted in Israelite identity (Hartin 2008, 295). However, unlike Matthew and James, it clearly has a concern for Gentiles. The ethic of the Torah is applied to the Gentile community as well as those from a Jewish background. This, again, is a means of socializing the people and creating one recognizable community.
In James, Hartin finds perfection as an important ethical marker (Hartin 2008, 297). The intention is that the people should be blameless, as the lamb offered to God was without blemish. Matthew also has a concept of perfection, which occurs as we imitate God in His concern for both good and bad (Hartin 2008, 299). Perfection in the Didache is also based on keeping Torah, and especially the Way of Life (Hartin 2008, 300). The people are to maintain purity above all. This creates their identity as people in a living relationship with God (Hartin 2008, 301). Hartin concludes that James, Matthew, and the Didache are alike in their call to perfection. However, while Matthew roots perfection in imitation of God, James focuses on the just works of care for others (Hartin 2008, 302). The Didache prescribes actions, but does not elaborate on them (Hartin 2008, 303). However, the actions are similar to the actions of God. This, says Hartin, is the standard for all three documents. The Christian is to be consistent, of a single mind (Hartin 2008, 305).
The twofold love command is also an important element in all three texts (Hartin 2008, 305). However, Hartin notes it is used in a different way in each. In James, the relationship of faith and works requires a conclusion that love for others must be practiced diligently. This is the predominant law of God's kingdom. In Matthew's Gospel, loving God and the neighbor is the means of fulfilling the Law and the prophets (Hartin 2008, 307). This embodies perfection, but based on the Scripture, as opposed to the more abstract concept of "kingdom" from James. In contrast, the Didache describes loving God and the neighbor in terms of remaining on the path of life (Hartin 2008, 307). The path of death, conversely, involves the lack of mercy.
Hartin next considers how the three documents fit into the context of the growing body of Christian literature. James works mostly with the conceptual world of the Septuagint and sayings of Jesus (Hartin 2008, 309). He takes them as harmonious and complementary. Matthew, though he uses sayings of Jesus extensively, uses them differently than James. "He preserves the character of the saying and transforms it only slightly to accord with other traditional material at his disposal and his theological vision" (Hartin 2008, 309). The Didache uses Jesus traditions less frequently, and, in Hartin's opinion, tends not to adjust the sayings (Hartin 2008, 310). Hartin notes that the Letter of Barnabas has a two ways section which likely derives from the same source used for the Didache (Hartin 2008, 310-311). Paul's conceptual framework may be contrasted to that of James. While Paul is more concerned with Jesus' work to complete salvation, James is more concerned that the Christian should actively live out the faith (Hartin 2008, 311). Counter to Paul, Matthew does not speak of slavery to sin or why we would not carry out God's law (Hartin 2008, 311-312). Matthew tends to focus on actions. Hartin observes that John gives few ethical instructions other than the need to love (Hartin 2008, 312).
Hartin concludes that Matthew, James, and the Didache each provides an ethical framework but that they differ in nature due to the time and context of their composition. He places James first, writing to communities which are essentially Israelite (Hartin 2008, 313). Matthew he sees next, in a context which welcomes and incorporates gentiles into the community (Hartin 2008, 314). Finally, the Didache, a few decades later, but from the same community as Matthew, reflects a more robust gentile Christian community.