Galatians 4:8-31

Paul sees what's happening and it doesn't make sense. Well, it makes sense because people are sinful and they turn away from God. However, they received the good news of the gospel and they turned to God, but now are turning back to their sinful ways. He encourages them to turn back to God and reminds them of how he initially brought the good news to them and how they received it. These people who are now trying to persuade them away from Jesus are doing this with ill intent and shouldn't be followed.

Paul goes on to give an example using the story of Abraham. He was barren, but was promised a child from God. When this wasn't happening, he had a child with Hagar, Sarah's servant. However, God's promise was through Sarah and the child born to her later, which was Isaac. These children are represented by two covenants with God, as Paul explains. There is one of slavery and one of freedom. Those Paul is talking to are described as children of promise like Isaac.