The early Christians had a Jewish background, and so with their new Christian identity, they had to wrestle with their Jewish identity as it related to the Jesus movement. Circumcision played an important role in maintaining Jewish identity. Genesis 17 portrays the establishment of circumcision as the sign of the Abrahamic covenant. Thus, circumcision was an important ritual throughout the history of Israel. When the Jesus movement gets going full steam after Jesus’ resurrection, the early followers began to question the relevance of circumcision for the new covenant people. This led to the Jerusalem council as depicted in Acts 15. The outcome of the council was that Jewish Christians could continue to practice circumcision if they wanted, but for Gentile Christians, circumcision was not required. Later, Paul and other leaders emphasized the circumcision of the heart as the sign of the new covenant (Rom 2:25-5:5; 1 Cor 7:17-20; Gal 5:1-15; 6:11-18; Eph 2:11-12; Phil 3).
Food laws also played a major role in maintaining Jewish identity. Hebrew scripture passages such as Leviticus 11:1-47 and Deuteronomy 14:2-20 describe the food instructions that the Israelites were to follow. These laws bound the Jewish people together and gave them a sense of ethnic identity. The early Christians believed that the gospel releases people from all prohibitions concerning food; however, many Jewish Christians struggled with participating in such liberty due to their past adherence to the food laws. As a result, the leaders of the early church needed to address the differences in conscience. Paul writes, “As for the one who is weak in faith, welcome him, but not to quarrel over opinions. One person believes he may eat anything, while the weak person eats only vegetables. Let not the one who eats despise the one who abstains and let not the one who abstains pass judgment on the one who eats, for God has welcomed him” (Rom 14:1-3 ESV).
Sabbath observance was another marker of Jewish identity. Sabbath keeping was established as one of the ten commandments as read in Exodus 20:8-11, and it is further stressed as a sign of the covenant in Exodus 31:14-17. The Christian church recognized the importance of Jesus’ resurrection, and so they observed a day of rest on the first day of the week in accordance with the day of Jesus’ resurrection (Acts 20:7). This day became known as the Lord’s day (Rev 1:10). This new view of sabbath was a challenge for the early Christians, but ultimately, they taught that sabbath rest was a symbol of Christ’s salvation of humanity. Thus, sabbath was not to be observed in a legalistic manner but people were to peacefully enter into Christ’s salvific rest (Heb 4:1).
Lastly, purity was a factor in maintaining Jewish identity. God had commanded the that the Israelites be consecrated or made pure before they could be in contact or near him (Ex19:10). Thus, God gave ritual purity laws and ritual cleansing laws that were to be followed, and ritual impurity was to be avoided. The Christian church determined that ritual purity was not required under the new covenant based on Jesus’ teaching which was more focused on moral impurity associated with thoughts, words and actions (Matt 15:11). However, some Christians still struggled with their Jewish identity regarding purity. For example, Peter had a temporary relapsed back into old ritual purity thought patterns in which he treated the Gentiles as unclean, and so he separated from them (Gal 2:14-15). Furthermore, Paul writes to Timothy and reminds him that “everything created by God is good, and nothing is to be rejected if it is received with thanksgiving, for it is made holy by the word of God prayer” (1 Tim 4:4).
 Archie T. Wright, “Jewish Identity, Beliefs, and Practices,” in The World of the New Testament: Cultural, Social, and Historical Contexts, eds. Joel B. Green and Lee Martin McDonald (Grand Rapids, MI: Baker Academic, 2017), 311-314. Wright,”Jewish Identity, Beliefs, and Practices,” 114-115. Wright,”Jewish Identity, Beliefs, and Practices,” 315.