Context: Galatians 4:21-31 climaxes Paul's argument against the Judaizers who are pressing Gentile believers to adopt circumcision and Torah-observance as necessary for covenant standing. Having already argued that the Abrahamic promise preceded and outranks Sinai (3:17-18), that the law was a temporary guardian (3:24-25), and that believers are sons and heirs through the Spirit (4:1-7), Paul now deploys a Scripture-based proof from the Genesis narrative itself. He addresses those who "desire to be under the law" (v. 21) and asks them to listen to what the law actually says. What follows is the NT's most overt two-covenants passage: Hagar and Sarah are re-read as standing for "two covenants" (δύο διαθῆκαι), with Hagar-Sinai-present-Jerusalem-slavery set against Sarah-Jerusalem-above-freedom-promise. The passage operates by ἀλληγορούμενα ("things spoken allegorically," v. 24) — a deliberate, second-sense reading Paul authorizes by inspiration — and ends with a citation of Genesis 21:10 ("Cast out the slave woman and her son") turned into an apostolic imperative against the Judaizers. The rhetorical force is unmistakable: to submit to Sinai as the basis of covenant standing is to identify oneself with Hagar and Ishmael, not with Sarah and Isaac — not with the children of promise but with the children of the flesh.
Greek Key Terms:
OT-to-OT Development: Paul's allegory exploits narrative features that are already theologically marked in Genesis. Ishmael is born "according to the flesh" (κατὰ σάρκα) from Hagar the Egyptian slave (Genesis 16:1-4, 15); Isaac is born "through promise" (δι᾽ ἐπαγγελίας) from Sarah the free woman after supernatural intervention (Genesis 17:15-21; 18:10-14; 21:1-7). Genesis 21:9-12 narrates Ishmael "mocking" Isaac and Sarah's demand that the slave woman and her son be cast out — with God's explicit endorsement: "through Isaac shall your offspring be named." The trajectory of the Pentateuch places the covenant line exclusively through Isaac, not Ishmael. The later prophets develop "Jerusalem" typologically: the "present Jerusalem" enslaved to Sinai's law-covenant (and, by Paul's day, politically enslaved to Rome) stands over against "the Jerusalem that is above" — the eschatological city promised in Isaiah 54:1 (quoted in v. 27), where the barren one (Sarah/restored Zion) rejoices with more children than she who has a husband. Isaiah 54 itself is part of the Servant-Song complex that ties post-exilic restoration to the New Covenant ministry of the Servant (Isaiah 53-55). Paul reads Genesis and Isaiah together: Sarah's laughter prefigures Zion's eschatological joy.
Connections:
Christological Connection: Paul's allegory makes the two-covenants antithesis explicit and inescapable. The two covenants are not two complementary administrations of grace that can coexist as grounds of covenant standing; they are two mothers producing two different kinds of children. One woman bears children for slavery (δουλεία), the other for freedom (ἐλευθερία); one corresponds to Mount Sinai and the present Jerusalem, the other to the Jerusalem above; one child is born "according to the flesh" through natural means, the other "through promise" through supernatural intervention. To anchor covenant identity in Sinai is to be Hagar's child, not Sarah's. Paul's "anti-typology" here is Greidanus's Contrast method at full strength: the old covenant does not merely prefigure the new; it is opposed to the new at the level of covenantal offspring.
Christ is the one who secures the Sarah-Jerusalem-above-freedom side of the antithesis. It is His incarnation ("born of woman, born under the law," 4:4), His redemptive substitution ("to redeem those who were under the law," 4:5), and His Spirit ("God has sent the Spirit of his Son into our hearts, crying, 'Abba! Father!'" 4:6) that make believers children of the free woman. He is the "Seed" of the Abrahamic promise (3:16) whose arrival terminates the guardian-role of the law (3:24-25). The barren woman of Isaiah 54 — Zion, Sarah, the Jerusalem above — rejoices with many children precisely because Christ has fulfilled the promise and opened the covenant to the Gentiles through faith (3:14, 28-29). The Judaizers' attempt to re-impose Sinai as the covenantal ground is therefore not a minor theological error; it is ecclesial repositioning under the wrong mother.
The already/not-yet dimension is visible in the "Jerusalem above" language (v. 26). Believers are already children of the free woman, already citizens of the heavenly Jerusalem (Philippians 3:20), already freed "for freedom" (Galatians 5:1). But the Jerusalem above is "coming down out of heaven" (Revelation 21:2) — the consummation awaits. The casting out of the slave woman (v. 30) is a present imperative for the Galatian churches (expel the Judaizing teaching) and an eschatological guarantee that the two covenants will not finally coexist as rival covenantal grounds: the new covenant in Christ's blood is the covenantal ground of the age to come.
Connection Method(s): Contrast (primary) — this is the textbook NT Contrast passage, where Paul does not merely escalate Sinai into the new covenant but expels it from the covenantal inheritance ("cast out the slave woman and her son," v. 30). The two covenants are antithetically paired (slavery vs. freedom, flesh vs. promise, present Jerusalem vs. Jerusalem above), ratifying the "Contrast" primary method of this trajectory. Also Promise-Fulfillment — Isaac's birth "through promise" prefigures the believers who are born through the Spirit-and-promise in Christ (v. 28), with Isaiah 54:1 cited as prophetic confirmation of the barren-woman-rejoicing eschatological fulfillment. Also Typology (Backward-Looking) — Paul's ἀλληγορούμενα reading identifies Hagar/Sarah as types only from the retrospective vantage of the gospel (not from indicators in Genesis itself); correspondence (two mothers → two covenants), historicity (both women historical), escalation (freedom surpassing slavery, promise surpassing flesh) are all met, but the forward-pointingness is supplied by apostolic inspiration, not by features in the Genesis narrative alone. NOT Typology alone: the Contrast dimension is primary and must not be subordinated — the allegory's rhetorical force depends on opposition, not just escalation.
Trajectory Table: 164 - Two Covenants (Law and Promise)