So Peter opened his mouth and said: “Truly I understand that God shows no partiality, but in every nation anyone who fears him and does what is right is acceptable to him. As for the word that he sent to Israel, preaching good news of peace through Jesus Christ (he is Lord of all), you yourselves know what happened throughout all Judea, beginning from Galilee after the baptism that John proclaimed: how God anointed Jesus of Nazareth with the Holy Spirit and with power. He went about doing good and healing all who were oppressed by the devil, for God was with him. And we are witnesses of all that he did both in the country of the Jews and in Jerusalem. They put him to death by hanging him on a tree, but God raised him on the third day and made him to appear, not to all the people but to us who had been chosen by God as witnesses, who ate and drank with him after he rose from the dead. And he commanded us to preach to the people and to testify that he is the one appointed by God to be judge of the living and the dead. To him all the prophets bear witness that everyone who believes in him receives forgiveness of sins through his name.”
While Peter was still saying these things, the Holy Spirit fell on all who heard the word. And the believers from among the circumcised who had come with Peter were amazed, because the gift of the Holy Spirit was poured out even on the Gentiles. For they were hearing them speaking in tongues and extolling God. Then Peter declared, “Can anyone withhold water for baptizing these people, who have received the Holy Spirit just as we have?” And he commanded them to be baptized in the name of Jesus Christ. Then they asked him to remain for some days. Acts 9:34-48.
For centuries, in order to become a Jew, men had to be circumcised. And that is a pretty high barrier to entry. But God changed all that by pouring out His spirit on thesem non-Jews, known as Gentiles. The Good News, that Jesus has taken away the sin of the world, is available to anyone, from any tribe or nation. In this way, Abraham would now be the father of many nations.
When Jesus said to go into all the world and make disciples of all nations, it really didn’t click right away that this meant that someone from a pagan culture could end up as your brother in Christ. And even for years after this event, there would be Jews who insisted that the Gentiles had to be circumcised to enter the kingdom of God. This is not unlike the blindspot America’s founders had about the ramifications of all men being created equal.
What the constitution could not do (change people’s hearts), the Holy Spirit can. He makes us one in Christ, no matter where we come from. He accepts us all, so must we do the same. For us, it may be our denominational walls that separate us. But God does not recognize those walls, because He didn’t build them.