What does Galatians 2:4 mean?

When the church was born, most of the new believers in Jesus were Jewish people who had grown up following the law of Moses. Males among this group would have been circumcised at a young age; this distinctive practice is often used as a shorthand for the entire law of Moses. As faithful Jews, these early Christians would have been raised to avoid associating with non-Jewish people—Gentiles—in specific situations.

After these people believed in Jesus, many of them continued to follow at least some of the practices of the Law. But what if you told the good news of salvation through faith in Jesus to someone who had never been Jewish, had never followed the Law? What did they have to "do" to be included in this new thing called Christianity?

Paul preached what Jesus gave to him to say: these non-Jewish believers didn't have to "do" anything differently to be saved and included. That, in fact, is a core message of the gospel, that Jesus already did it all on the cross. So, in the case of Gentile believers, they didn't need to be circumcised as if they were joining Judaism under the law of Moses (Exodus 12:48). Paul has reported that the most influential Christian leaders in Jerusalem, all Jewish and mostly apostles, agreed with him. They did not require, for instance, that Paul's Greek friend Titus be circumcised to be saved (Galatians 2:3).

But some others in Jerusalem did think Titus should be circumcised. Paul called these men "false brothers." Their position is stated clearly in Acts 15:1: "Unless you are circumcised according to the custom of Moses, you cannot be saved." Paul said emphatically: That is not the gospel of Jesus. That is false. This is a crucial aspect of how the New Testament explains salvation; Scripture is explicitly clear that any attempt to add works, rituals, or any other requirements to salvation by grace through faith is false and worthy of condemnation (Galatians 1:8–9).

Paul even accuses those teaching a requirement of works in the Christian church of being spies, practicing espionage for the purpose of taking away the freedom Christ gives and replacing it with a slavery to the Law.