“These things are illustrations, for the women represent the two covenants. One is from Mount Sinai and bears children into slavery–this is Hagar” (Galatians 4:24 HCSB).
Although Abraham was the father of many children, there are two sons of Abraham who are particularly important. The first was Ishmael, the son who was born to Abraham through his marital relationship with a servant named Hagar. The other was Isaac, the son of God’s promise who was born to Abraham and his wife Sarah. One commentary offers some background information on the birth of these sons that can help us understand and apply the final verses of Galatians chapter four…
“God had promised that Abraham would have a son, even though he and Sarah were too old, naturally speaking, to have children. Abraham believed God and thus was justified (Gen_15:1-6). Sometime afterward, Sarah became discouraged, waiting for the promised son, and suggested that Abraham should have a child by her slave-girl, Hagar. Abraham followed her advice, and Ishmael was born. This was not the heir promised by God, but the son of Abraham’s impatience, carnality, and lack of trust (Gen. 16).” (1)
Galatians 4:24 tells us that these sons illustrate the difference between the Old Covenant (represented by Ishmael) and the New Covenant (represented by Isaac). The Old Covenant placed its followers in a type of bondage, much as Hagar was identified as a “bondwoman” earlier in Galatians 4:22. In other words, those who sought to approach God via the works of the Law had to continue those efforts or face rejection. In contrast, the New Covenant is associated with the son born through Sarah. She represents the “freewoman” of Galatians 4:22.
The experience of these women provide us with an allegory that clarifies the idea behind this passage. Nevertheless, its important to recognize that the Old Testament account of Abraham, Sarah, Hagar, Ishmael, and Isaac is not an allegory itself. Instead, these verses present us with an illustration based on the historic account of these individuals. (2)
So Hagar served as a model that represented what the false teachers of Galatia sought to accomplish. Just as her son was born as a result of human effort, these legalists sought to compel the Galatians to seek justification with God on the basis of their efforts as well. On the other hand, Sarah’s offspring exemplified the message of Galatians 4:7: “Therefore you are no longer a slave but a son, and if a son, then an heir of God through Christ.”
(1) William Macdonald, Believer’s Bible Commentary Edited by Arthur Farstad Thomas Nelson Publishers p.1889
(2) We might use other literary terms such as typology, analogy, or “figurative language” help to communicate a similar idea.