Galatians 4:22 For it is written that Abraham had two sons, one by a slave woman and one by a free woman.
Abraham had two sons, just for this illustration, He actually had six more children (Genesis 25:2) One by a handmaid. Ishmael was by Hagar, Sarah’s servant, who represented the covenant the Jewish nation was under the bondage of the law. The other by a free woman. Isaac was by Sarah, Abraham’s proper and lawful wife, who was mistress of the family, and represented in figure the new covenant in Grace, for all believers, Gentiles as well as Jews, God through Paul is vindicating his Gospel plan with a clear illustration. Hagar was a slave in bondage to Sarah, she represents the The nation of Israel in bondage to the law and under the old covenant. While Sarah the free woman in that She was illegally married to Abraham. Thus Her descendant Isaac represented the new covenant of Grace. One born according to the flesh and the other born according to the promise. Let scripture speak for itself.