Early and Diverging Views of Christians and Jews.
Divergent understandings of Judaism were found among Christians in the mid-second century. At one extreme were the Jewish-Christian adoptionists, who continued to worship the God of Israel as the one true God and Jesus as his Son. These Christians strove to keep the Jewish Law in all its particulars, including such things as circumcision, Sabbath observance, and kosher food laws.
At the other extreme was Marcion, who claimed that the Jewish God was an inferior deity, that Jesus had no relationship to this God but represented the higher true God, and that the Jewish Law was a form of bondage meant for the Jews but absolutely not for Christians.
These disparate views did not spring from the ground full-grown in the middle of the second century, of course. Each had a long prehistory of its own. The Jewish-Christian adoptionists claimed to find their views in their Gospel, which was very similar to the Gospel of Matthew, where Jesus says that his followers are to keep the entire Law even better than the scribes and the Pharisees (Matthew 5:17-20). Marcion claimed to find his views in the writings of Paul, who urged the Galatians not to become circumcised, because if they did they would be obliged to follow the entire Law (Galatians 5: 2-3).
These differences raise an interesting hypothetical question. Suppose Matthew and Paul themselves had been brought together and instructed to produce a joint position paper on whether believers in Jesus were to follow the Jewish Law. Would they have been able to hammer out a consensus?
Bart D. Ehrman, The New Testament: A Historical Introduction to the Early Christian Writings, page 437. This is highly recommended:
Dr Bart Ehrman is an American New Testament scholar focusing on textual criticism of the New Testament, the historical Jesus, the origins and development of early Christianity. He has written and edited 30 books, including three college textbooks. He has also authored six New York Times best sellers.