NOTES for Gal 4:11-31
As can be seen, the main problem of the Galatian Christians was that, in Paul's own words, they wanted to be "under the authority of the Torah" ("under the law," v. 21). Such a desire could well have arisen in them after Paul, whom, according to his own testimony, they had received "as a messenger of God" (vv. 12-14), had left them. The freedom of the Kingdom to which the apostle had evidently testified to them could have seemed excessive to the Galatians, as sometimes happens with new converts who are looking for a "firm hand." And then Paul's place was quite naturally taken by those whom the apostle calls "unclean zealots" (vv. 17-18). In that case, the already mentioned lust for power of these new "pastors," their claims to exclusivity, and the fact that, despite all this, the Galatian church treated them with respect and even, it seems, with a certain fear, become completely understandable and explainable.
Meanwhile Paul offers them a parable based on material from the book of Genesis. He reminds them of the well-known story of the birth of Ishmael, who was born before Isaac, although he was not Abraham's son by Sarah, the son about whom God had spoken to Abraham. That is why the apostle says that one of the two sons was born "according to the flesh," that is, exclusively according to human will, while the other was born "according to the promise," in accordance with the promise given by God (vv. 22-23). Paul compares these two sons with two unions, or "covenants": the former, based on the Torah and on following the law, and the new one, based on faithfulness to God and on the promises that had been given already to Abraham and were fulfilled, according to the apostle's word, only now, after the coming of the Messiah (vv. 24-31).
At first glance, such a contrast divides the old and new covenants just as it divides the old and new people of God. But the apostle is not speaking about division. He only wants to emphasize the fact that the former union, concluded already with Abraham, can receive its fullness only in the new, messianic union that is concluded with God through Jesus Christ. The earlier unions are not canceled or devalued, but in order to make use of everything they can give, one must turn to the One in whom they received their fullness.