Donald Hagner’s article on Jewish Christianity in the Dictionary of the Later New Testament provides a summary of the theology of Jewish Christianity. The first issue Hagner discusses is the Law and Christian Life. The Jewish community in Acts appears to have continued to keep the Law. As Jews, there was no real disconnect between keeping the law and salvation. The Temple was the main location of evangelism. This evangelism did not attack the Temple or the priesthood, but seems to use temple worship as an opportunity to reach priests and Pharisees. From the beginning of his Gentile mission, Paul had to deal with Judaizers who argued that Gentiles ought to keep the law.
James Dunn agrees with this summary in his recent Neither Jew nor Greek (Eerdmans, 2015). In this book Dunn tracks the shift from an entirely Jewish Church in early Acts to a more or less Gentile church by the fourth century A.D. He discusses each of the books int he Jewish Christian literature and concludes they all represent some form of Jewish Christianity. With the possible exception of the epistles of John, each of these books are indebted to the Jewish Law.
The Jewish Christian literature displays a range of belief on the issue of Law. Hebrews which is has the most to say about the Law and the role of the law in the present age. The Law itself is rarely addressed in Hebrews, and the Hebrew Bible as a whole is treated as foundational for understanding Jesus. The writer of Hebrews does not argue that Jesus “cancels the Law,” but rather that the law is most fully understood in the light of Jesus and his sacrifice. There is a certain amount of “supersession” in Hebrews – what Jesus did goes beyond the Law, therefore the only way to “do the Law” is to read it through the lens of Jesus.
James seems to have been a law-keeping Jew throughout his life. The book of Acts describes James as the leader of a robust church in Jerusalem with many priests and Pharisees, all of whom were “zealous for the law” (Acts 21:20). In James’ letter a short discussion on keeping the “royal law” (love your neighbor), and in the context James points out that breaking one Law makes one guilty of the whole law (James 2:8-10).
The most extreme example of Jewish Christians and the Law were the Ebionites. Some caution is needed here since we do not have anything that represents their own writings (possibly the Pseudo-Clementines, but this literature may reflect another early Christian group). We really only know of the Ebionites through the impression they left on the theological conversations of the second and third centuries. While it is likely that they are a sub-Christian sect (and usually included in lists of heretics), they claimed to be the real followers of Christ. They required complete obedience to the laws, including circumcision, food laws and Sabbath (Eusebius HE 3.27, cf., Skarsaune, 437-8). They considered Paul’s view of the Law as inadequate and held James as the leader of the church.
Applying these observations to the New Testament, it is possible to call all the literature “Jewish” although the Pauline letters are clear that the Law is not to be imposed on Gentiles. There is no statement in the Jewish-Christian literature that Gentiles ought to keep the Law, but it is clear that Hebrews and James especially are interested in the interpretation and application of the Hebrew Bible in the present age.
But what about 1 Peter or the letters of John? Are they more or less interested in the continuing application of the Law to the Christian in the present age? Since Paul does discuss the Law at in many of his letters (Romans and Galatians especially), this question might be better asked as “how does the Jewish-Christian literature use the Law differently than Paul?”
Bibliography: Donald Hagner, “Jewish Christianity,” pages in the Dictionary of the Later New Testament (Downers Grove, Ill.: InterVarsity, 1997); Oskar Skarsaune, “The Ebionites,” pages 419-62 in Jewish Believers in Jesus (Peabody, Mass.: Hendrickson, 2007).