Two Covenants, Two Kinds of Children, One God
There are not two Gods, but one God whose covenant has fundamentally changed how His children exist and relate to Him. Remarkably in Galatians 4 — Paul reaches back into a beloved narrative in Scripture and reads it as an allegory. Two women in Abraham's household, two sons, two entirely different origins, two entirely different destinies. And in doing so, he gives us one of the most clarifying pictures in the New Testament of what it actually means to live under each covenant.
"These things," Paul writes, "are being taken allegorically, for these women are two covenants" (Galatians 4:24). Hagar represents the covenant from Mount Sinai — the very same mountain of fire and thunder we stood before in the last section, Two Mountains, Two Mediators, One God — bearing children into slavery. Sarah represents the covenant of promise, bearing children into freedom.
The contrast begins at the point of origin. Hagar's son, Ishmael, was born according to the flesh — the product of human effort, Abraham's impatience, and Sarah's strategy to accomplish through natural means what God had promised through supernatural ones. Ishmael was not illegitimate in the ordinary sense; he was the deliberate result of human striving to produce what only grace could deliver. This is precisely Paul's portrait of law-keeping.
The person who returns to the Law to obtain righteousness, life, or standing before God is doing exactly what Abraham did with Hagar — taking hold of the promise through fleshly means, producing a child that can never be the heir. Sarah's son Isaac, by contrast, was born through promise (Galatians 4:23). Nothing in the natural order could produce him — Sarah was barren, both she and Abraham were far past the age of childbearing — and yet God spoke, and life came from what was as good as dead. That is the Greek ἐπαγγελία (epangelia), the promise, doing what no law or human effort ever could.
Paul then maps these two women onto two types of Jerusalem. Hagar corresponds to the present Jerusalem — the Jerusalem of his day, the center of the Mosaic system, the city still organized around temple, sacrifice, and law — and she is in slavery with her children (Galatians 4:25). Sarah corresponds to the Jerusalem above, which is free, and she is our mother (Galatians 4:26).
This is a staggering claim. The believer's true city, true lineage, and true identity does not descend from the earthly administration of the Law — it descends from the heavenly, from the promise, from what God alone has done. To go back to the Law is not merely a theological error; it is, in Paul's framework, a return to the identity of the slave woman's child. It is to swap inheritance for bondage, sonship for servitude, and promise for performance.
What makes this section of Galatians so searching is Paul's observation that the son born of the flesh persecuted the son born of the Spirit — and so it is now (Galatians 4:29). This pattern has never stopped. Those who build their religious life on fleshly effort, on the performance of commands, on the visible and measurable metrics of law-keeping, have historically been the ones most resistant to — and most hostile toward — those who live from pure grace.
It was the most law-observant religious leaders of Jesus' day who crucified Him. It was the Judaizers in Galatia who were enslaving new believers. The son of the slave woman does not celebrate the son of the free woman; he persecutes him. Law-based religion and grace-based sonship have never peacefully coexisted, because they represent two entirely different answers to the question of how a human being stands before God.
Paul's conclusion is unambiguous: "Cast out the slave woman and her son, for the son of the slave woman shall not inherit with the son of the free woman" (Galatians 4:30). This is not a polite suggestion toward theological balance — it is a declaration of incompatibility. You cannot build a life that is half Hagar and half Sarah, half law and half grace, half striving and half resting in promise.
The two cannot coexist as co-heirs because they represent mutually exclusive foundations. And then Paul drives the application home in the very next verse: "So, brothers, we are not children of the slave but of the free woman" (Galatians 4:31). The identity of the believer is settled. We are Isaac's kind — children of promise, born of the Spirit, heirs not through an earthly lineage or because we earned it but because the Father spoke it into existence over barren ground.
This is the freedom that the new covenant inaugurates, and it is the freedom Paul spends the entire letter of Galatians defending. For it is not merely a freedom from something — from the Law, from condemnation, from the exhausting cycle of performing to be loved — it is a freedom into something. Into sonship. Into love. Into inheritance. Into the life of the Jerusalem above, where the mediator is not a trembling servant but the risen Son, and where the children are not born of flesh and blood, of human effort but of promise, of the Spirit of the living God.