Expositor's Bible Commentary Commentary Galatians 4:29

"But as then he that was born after the flesh persecuted him [that was born] after the Spirit, so also it is now." — Galatians 4:29 (ASV)

In the third section of this treatment of the Hagar and Sarah story, Paul applies the allegory to all Christians, pointing out that because they are like Isaac, who had a supernatural birth, rather than like Ishmael, their experiences will be consistently similar to that of the younger son.

In the first place, they must expect persecution from their brother. Paul is referring to Ge 21:8–13, when, at the weaning of Isaac (he was about two years old and his half-brother Ishmael about seventeen), Ishmael began “mocking” Isaac. Thus Sarah asked that Hagar and her son be sent away. So it is today, says Paul. True Christians will be persecuted (cf. Matthew 5:10–12; 1 Thessalonians 3:1–4; 2 Timothy 3:12; 1 Peter 4:12—13). And the remarkable thing is that this will not always be by the world but indeed more often by their half-brothers—the unbelieving but religious people in the nominal church. This is the lesson of history. It was the Jews who killed the prophets, not the Gentiles. It was the Pharisees and other religious leaders who opposed Jesus and instigated his execution, which was carried out by the Romans. Paul’s fiercest opponents were the fanatically religious Judaizers. Today the greatest enemies of the believing church are found among the members of the unbelieving church, the greatest opposition emanating from the pulpits and church hierarchies.