Galatians 4:31

Sarah's demand about Ishmael in Genesis 21:10 becomes a guideline (see Genesis 21:12) for dealing with the current son of the slave woman (anyone who refuses to abandon slavery to the law). God does not let those who try to be righteous through their own efforts share in his inheritance (see Romans 9:30–33). Those who come to God through Jesus Christ alone, by faith and not by following the law, are children of the free woman who inherit God's blessings.

Paul uses the story of Hagar and Sarah in 4:21–27 to explain the situation in Galatia. Isaac represents those born through God's promise (see 3:8) by the Spirit's power (3:2–5; see also Ephesians 1:13–14). These people trust in God for salvation through Christ by faith. Ishmael represents those who think following the law of Moses will make them acceptable to God (Galatians 3:10–11). This idea would have surprised the Judaizers, who believed they were Abraham's true children because they followed the law of Moses.

• Paul now returns to using Scripture to support his argument. He tells the story of two of Abraham's wives, Hagar and Sarah, and their children. He uses this story to show the difference between two types of people: those who are like slaves because they try to follow all the laws, and those who are free because they belong to Christ.

• Paul uses a special way of explaining Bible stories (called allegory) that Jewish teachers used in those days (see study note on 4:24). Paul was trained as a rabbi (see Acts 22:3) and could effectively debate the Judaizers using their own methods.