Because the New Testament is built on the Old Testament, this brings us to our passage this morning in Galatians 4:21-31. Here we will see on full display the gospel preached from the Old Testament. Paul helped found the churches in Galatia. He first preached the gospel to them. But now, the Judaizers (we could call them “legalizers” or “legalists”) were seeking to lead the Galatian church into a Christianized form of Judaism. They were proficient in the Old Testament Scriptures, but so was Paul.
In this passage, Paul is taking on the Judaizers on their own terms. He uses passages and stories that they know well in order to draw contrasts between the religion of works and the message of the gospel of grace. The non-Jewish or Gentile Galatian Christians believed that they needed to be like the Jews in order to be truly faithful to God. They needed to follow the letter of the law to truly be His children. So there was this tension between trying to fulfill the law themselves and believing the gospel of grace that Paul had taught them. That tension sets the stage for our passage this morning.