In March 2012, my pastor preached a sermon on Genesis 16 which relates the narrative of barren Sarah (Sarai) giving her handmaid Hagar to Abram (Abraham) to bare him a child. Hagar conceives Ishmael and despises Sarah. "And Sarai said unto Abram, My wrong be upon thee: I have given my maid into thy bosom; and when she saw that she had conceived, I was despised in her eyes: the Lord judge between me and thee. But Abram said unto Sarai, Behold, thy maid is in thy hand; do to her as it pleaseth thee. And when Sarai dealt hardly with he, she fled from her face," (Gen. 16:5-6).
In this story, Hagar represents the Covenant of Works and Sarah represents the Covenant of Grace: "For it is written, that Abraham had two sons, the one by the bondmaid, the other by a freewoman. But he who was of the bondwoman was born after the flesh; but he of the freewoman was by promise," (Gal. 4:22-23).
Sarah is the first wife, and Hagar is submissive to her mistress; this same relationship of submission is reflected in the Gospel and the law. "Knowing that a man is not justified by the works of the law, but by the faith of Jesus Christ, even we have believed in Jesus Christ, that we might be justified by the faith of Christ, and not by the works of the law: for by the works of the law shall no flesh be justified," (Gal. 2:16). "Therefore by the deeds of the law there shall no flesh be justified in his sight: for by the law is the knowledge of sin," (Rom. 3:20).
"3. In the process of time the son of the bond-woman who was born after the flesh persecutes the son of the free-woman who was born after the Spirit; that is, in the virtue of the promise. Because of this the bond-woman and her son are cast out of the family and Isaac remains there as the only heir of his father's blessing.The apostle [Paul] affirms that these things were ordered by God in a typical relationship to gospel times and applies them as follows.Hagar was a type of Mount Sinai and the legal covenant established there. Ishmael was a type of the carnal seed of Abraham under that covenant. Sarah was a type of the new Jerusalem, the gospel church founded on the covenant of grace. Isaac was a type of the true members of that church who are born of the Spirit, being converted by the power of the Holy Spirit for the fulfilling of the promise of the Father to Jesus Christ the mediator. And the ejection of Hagar and Ishmael was to prefigure the abrogation of the Sinaitic covenant and the dissolving of the Jewish church-state so that the inheritance of spiritual blessings might be clearly passed down to the children of God by faith in Jesus Christ."
In his treatise, Cox argues that the Covenant of Grace has no outward sign or seal annexed to it (circumcision or baptism). The New Testament tells us that circumcision obligates man to keep the whole law, (Gal. 5:3); therefore, circumcision cannot give man an interest in the grace that justifies a sinner before God. Abraham himself did not obtain the terms of the Gospel by his carnal prerogative but was justified by his faith before he was circumcised. Abraham received circumcision not as a seal of his righteousness by faith or of the New Covenant, but of the righteousness of the faith which he had being yet uncircumcised. It was a seal of his paternal relationship to all believers though they were not circumcised because he is the father of all who believe, (Rom. 4:16).
"But that no man is justified by the law in the sight of God, it is evident: for, The just shall live by faith. And the law is not of faith: but, The man that doeth them shall live in them. Christ hath redeemed us from the curse of the law, being made a curse for us: for it is written, Cursed is every one that hangeth on a tree: That the blessing of Abraham might come on the Gentiles through Jesus Christ; that we might receive the promise of the Spirit through faith," (Gal. 3:10-14).