22. Two sons. Ishmael and Isaac (Gen. 16:15; 21:3). Paul now turns to “the law” (see on Gal. 4:21) itself for an illustration of the difference between bondage to “the law” and freedom in Christ. Inasmuch as portions of the Pentateuch were read every Sabbath in the synagogues (see V, 57), the books of Moses were well known to all Jews and to Gentiles who had been attending the synagogue services. The story related was a simple fact of Jewish history, but Paul uses it in an allegorical sense ( 24) to show the difference between being in bondage to the ceremonial system and enjoying the freedom that comes from faith in Jesus Christ. Abraham actually had more than two sons (see Gen. 25:1, 2), but Ishmael and Isaac were his eldest and most important sons. The false teachers had doubtless been emphasizing the blessing of being sons of Abraham (see on Gal. 3:7). Paul reminds the Galatians that Abraham had two sons and that one fell heir to the covenant promises while the other did not (Gen. 17:19-21). Simply being “sons” of Abraham was no guarantee of receiving the covenant promises.
A bondmaid. Hagar, an Egyptian slave (see on Gen. 16:1-4). Her son Ishmael was the son of Abraham—his firstborn, in fact—but because she was a bondmaid her son was, as it were, a bondson.
A freewoman. That is, Sarah, whose son Isaac was to inherit her freedom.