In the early days of the church, as recorded in the book of Acts, the apostles initially followed Jesus' command to focus on the lost sheep of the house of Israel, avoiding the way of the Gentiles. However, by the time of Pentecost, a significant shift occurred, marking the beginning of outreach to other nations. The conversion of Cornelius and his family highlighted God's call to the Gentiles, showing that unless God specifically called an individual, the general reaction of Gentiles to the gospel mirrored that of many Jews—often resulting in persecution. As the apostles, including Paul and Barnabas, preached in Gentile areas such as Antioch in Pisidia and Iconium, they encountered mixed responses. Many Gentiles were glad to hear the message, and those appointed to eternal life believed, causing the word of the Lord to spread throughout the regions. Yet, opposition arose as unbelieving Jews stirred up Gentiles, poisoning their minds and inciting violence against the apostles, leading to events such as the stoning of Paul in Lystra. Despite such resistance, the apostles persisted, reporting back to the church in Antioch that God had opened the door of faith to the Gentiles. A significant controversy emerged within the church regarding the requirements for Gentile converts, as some from Judea insisted on circumcision and adherence to the law of Moses for salvation. This led to a pivotal council in Jerusalem, described in Acts 15, where Paul, Barnabas, and others reported the conversion of the Gentiles, bringing great joy to the brethren. Peter emphasized that God made no distinction between Jews and Gentiles, purifying their hearts by faith and granting them the Holy Spirit. James, in his judgment, declared that they should not trouble Gentile converts with additional burdens, instead instructing them to abstain from things polluted by idols, sexual immorality, things strangled, and blood. This decision, influenced by Jesus' guidance through James, resolved the underlying issues at that time, allowing the church to settle into a more peaceful routine through local teachings and Bible studies.

The conversion of Cornelius, a Roman centurion, marks a pivotal moment in the progression of the gospel beyond Jerusalem, as detailed in chapter 10 and reiterated in chapter 11. This event, spanning 66 verses, underscores its significance, revealing the first major realization by the church that Gentiles were to be accepted into full fellowship with Jews. Unlike previous instances where Gentile conversions were peripheral, such as those in Samaria or the Ethiopian eunuch who had ties to Judaism, Cornelius had no prior religious connection to Judaism, making this a direct outreach to Gentiles. This incident addresses the church's initial resistance to evangelizing Gentiles and demonstrates that it was God Himself who orchestrated this shift in understanding. Surprisingly, God chose Peter, not Paul, to initiate this change, leveraging Peter's influence within the Jerusalem church to ensure acceptance. Peter's own ingrained Jewish scruples are evident, yet through divine intervention, including a vision instructing him not to call any man common or unclean, he comes to perceive that God shows no partiality, accepting whoever fears Him and works righteousness from every nation. The conversion of Cornelius and his household, accompanied by the outpouring of the Holy Spirit and their subsequent baptism, astonished the Jewish believers present, confirming that Gentiles received the same gift as the Jews at Pentecost. This event, paralleled with the Day of Pentecost in its significance, opened salvation to the vast majority of the world's population, fundamentally altering the church's direction and outreach. In Jerusalem, while the leadership accepted the validity of Gentile conversions, objections persisted among the broader Jewish congregation, particularly over Peter associating and eating with uncircumcised men. Peter recounted the divine guidance and events leading to Cornelius' conversion, leading to a temporary silencing of objections as they glorified God for granting repentance to life to the Gentiles. However, many unresolved questions about practices and fellowship remained, setting the stage for future challenges within the early church.

The issue of Gentile converts significantly impacted the early church, creating tension and division due to cultural and spiritual differences with the Israelite members. In Ephesians 2:10-18, it is evident that Gentiles, once far off and without Christ, were brought near through His blood, breaking down the wall of separation between Jew and Gentile to create one new man in Him. This reconciliation aimed to unite both groups into one body through the cross, granting them equal access to the Father by one Spirit. However, the Gentiles' lack of familiarity with the covenants and God's purpose, stretching back to Abraham, Isaac, and Jacob, led to misunderstandings and irritation on both sides, as the Israelites often felt superior due to their historical relationship with God. In Acts 15, a major dispute arose when certain men from Judea insisted that Gentile converts must be circumcised according to the custom of Moses to be saved, and some believing Pharisees argued it was necessary to command Gentiles to keep the law of Moses. Peter countered this by stating that God made no distinction between Jews and Gentiles, purifying their hearts by faith, and questioned why a yoke unbearable to their ancestors should be placed on the disciples. He affirmed that salvation comes through the grace of the Lord Jesus Christ for both groups alike. This argument was among the most intense internal issues faced by the early church, exacerbated by the unprecedented number of Gentiles being added and the lack of apostolic experience with such a phenomenon. Historically, as seen in Exodus 12:48-49, God permitted Gentiles to participate in the Passover under the Old Covenant if circumcised, treating them as natives of the land with one law for both native-born and strangers. This foundation shows that integrating Gentiles was not entirely new, but the scale and personal invitation by God in the New Testament era caused significant adjustment challenges for the Israelite church members, leading to heated disputes and dissension as they grappled with these changes.