The first Christians were practising Jews. It took time before the revolution, which was their belief in Jesus, established a new relationship with Judaism and there was a bitter internal conflict in the Church. Judaism was not a monolithic system—Pharisees, Sadducees, Essenes, and perhaps Samaritans being among the diversities. According to Acts 2: 46 the apostles frequented the Temple and a number of the Pharisees (Acts 15: 5) had joined the Church. The common element that bound these early Christians together was their belief that the Messiah was Jesus and that the scriptures were fulfilled in him. There was a major crisis when Paul, the former Pharisee, engaged in large-scale evangelization of Gentiles. It was his conviction that Jesus was not just the Jewish Messiah, and Christianity was not a kind of reformed Judaism. Salvation was offered to all mankind by Jesus, crucified and risen, and the Jewish Law was not an obligation for converted Gentiles. Some of Paul's Christian opponents in Jerusalem feared that this liberalism would lead to the abandonment of ethical standards of behaviour altogether. They continued to observe the whole Law and were Christian Jews rather than Jewish Christians. Others just wanted to go on observing the dietary habits of a lifetime for themselves and were prepared to accept a compromise; indeed Paul's own practice was a compromise—he observed at least part of the Law himself (e.g. in entering the Temple, after purifying himself, Acts 21: 26) while fighting to ensure the Gentiles' exemption from it. After the destruction of Jerusalem in 70 CE, the future for the Church was in Paul's Gentile Christianity, but the controversies in the gospels of Matthew, Luke, and John suggest that Jewish influence in the Church was still a force up to 100 CE. It is also the period when the Jewish-Christian epistle of James was written. But from the beginning of the 2nd cent., survivors of Jewish Christianity were marginalized into the Ebionites and Nazoreans, whose works are quoted by Origen and Jerome. The former group had an adoptionist Christology. Within the NT the epistle of James is the most obviously Jewish document; there are only two references to Christ (1: 1 and 2: 1), both of which could have been later Christian additions to a Jewish writing. James's examples of patience under suffering are from OT prophets and Job, not Jesus (5: 10 f.). The Revelation to John is certainly indebted to Jewish Christianity; it owes its imagery and style to Ezekiel and Daniel, and its acceptance into the Church was slow and reluctant on account of its alien apocalyptic character. The Church did not deny its own Jewish roots and Rom. 9–11 was there to remind the winning side that what God had promised in his covenant would embrace both Jews and Christians alike: but there were extremists who were at the opposite pole to the Ebionites; they were Marcion and his followers, who rejected the continuing validity of the OT and even much of the NT. Paul's epistles and a truncated gospel of Luke were their minuscule scriptures.
There are also NT writings with a Jewish background which occupy a mediating position in the Church. Thus the gospel of Matthew is heavily indebted to the OT and emphasizes the validity of the Law, but Matthew's Christology in which Jesus is identified with Wisdom (Matthew 11: 19; 23: 34–6) goes beyond the adoptionism of the Ebionites. The epistle to the Hebrews is thoroughly Jewish in tone, but is hostile to the Temple cult, as were the Ebionites (the Temple did not exist after 70 CE) but the epistle dismisses the (Ebionite) view that Christ could be accorded the status of an angel (Heb. 1: 4–2: 18).