Albert Barnes 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)

But as then he that was born after the flesh—this refers to Ishmael .

Persecuted him that was born after the Spirit—this refers to Isaac. The phrase "after the Spirit" here is synonymous with "according to the promise" in the previous verse. It stands in contrast to the phrase "after the flesh" and means that Isaac's birth was by the special or miraculous agency of God (see Romans 4); it was not in the ordinary course of events.

The persecution mentioned here was the injurious treatment Isaac received from Ishmael, or the opposition that existed between them. Paul's particular reference is undoubtedly to Genesis 21:9, where it is said that Sarah saw the son of Hagar the Egyptian, which she had borne unto Abraham, mocking. It was because of this, and at Sarah's special request, that Hagar and her son were expelled from Abraham's house (Genesis 21:10).

Even so it is now. This means that Christians, the children of the promise, are persecuted by the Jews—the inhabitants of Jerusalem, "as it now is" ()—who are uninterested in the promises, just as Ishmael was.

For an illustration of this, see Paley's Horae Pauline, on this Epistle (No. V). Dr. Paley has remarked that it does not appear that the apostle Paul was ever attacked by the Gentiles unless they were first stirred up by the Jews, except in two instances.

One of these instances was at Philippi, after the cure of the Pythoness (Acts 16:19), and the other at Ephesus, at the instigation of Demetrius (Acts 19:24).

The persecutions of Christians, therefore, arose mainly from the Jews—from those who were in bondage to the law and to rites and customs. Paul's allusion here to the persecution that Isaac, the free-born son, endured is exceedingly pertinent and fitting.