Van de Sandt, Huub. "Chapter Fourteen: Law and Ethics in Matthew's Antitheses and James's Letter: A Reorientation of Halakhah in Line with the Jewish Two Ways 3:1-6." 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, 315-338.
Van de Sandt observes the common opinion that Matthew 5:17-48 bears a strong similarity to the thought world of James (Van de Sandt 2008, 315). Their view of the Mosaic law, the goal of righteousness, and the concept of righteousness based on careful observance of the law are quite similar. Rather than posit a dependence between Matthew and James, Van de Sandt proposes that both texts are strongly oriented toward the Jewish Two Ways material found, among other witnesses, in Didache 3.1-6 (Van de Sandt 2008, 136). This material probably antedated the Didache, as evidenced by its inclusion in different variations in other early documents (Van de Sandt 2008, 317).
Van de Sandt breaks the text of Didache 3:1-6 into its component clauses, analyzing the overall structure. He observes that the bulk is divided into parallel couplets of a sin we would consider less serious leading to one we would see as more serious (Van de Sandt 2008, 319). The pattern, as Van de Sandt illustrates, is relatively common in rabbinic thought.
Though Matthew 5:17-48, and the surrounding passages, bear a resemblance to Luke 6:20-49, leading to much consensus that both authors relied on a Q source, Van de Sandt finds significant connections of Matthew 5 to the passage in Didache 3 (Van de Sandt 2008, 324). The underlying structure, with the "minor" offense followed by the "major" offense is alike, though in Matthew there is further elaboration. Both texts roundly affirm the necessity of the Law (Van de Sandt 2008, 327). Both the least and the greatest commands are valid. Matthew and the Didache both build the argument on precepts from the Decalogue (Van de Sandt 2008, 329). The topical arrangement is also significant, as the lighter command comes first and the heavier second (Van de Sandt 2008, 330).
Van de Sandt also compares James with Didache 3:1-6. In particular, he finds James 1:13-15 and 1:19-21 to correspond to the Didache's ethical material (Van de Sandt 2008, 331). In James, the desire leads to sin, which leads to death. The minor offense leads to the more serious one. Both documents describe the progression in terms of giving birth. As with Matthew and the Didache, James advocates a careful obedience to God's law (Van de Sandt 2008, 332). All of life is to be an expression of the command of God to love one another (Van de Sandt 2008, 333).
Van de Sandt observes a possible development of thought between that of Didache 3 and Matthew 5. In Matthew 5, the existing commands are intensified, while in Didache 3 existing commands are simply serialized (Van de Sandt 2008, 335). The same may be said of James, where a "small" sin becomes equated with murder, war, or adultery (Van de Sandt 2008, 336).