When reading the Old Testament, it can seem that God dealt with Abraham and Moses under two entirely different principles.
Abraham received a promise and believed God, while Israel received commandments accompanied by blessings and curses. This contrast raises an important theological question: Did the Mosaic covenant introduce a different means of obtaining righteousness before God?
Paul addresses this question in Galatians 3:17, explaining that the law, given 430 years after the promise to Abraham, could not annul that promise. The arrival of the Mosaic covenant did not replace salvation by grace through faith with salvation through obedience.
Nevertheless, understanding how law and gospel functioned under Moses requires careful distinctions.
The Mosaic Covenant and the Promise
The Mosaic covenant was a distinct covenant established with Israel as a nation, containing commandments, ceremonies, and blessings and curses associated with Israel’s obedience (Exo 19:5–6; Deut 28). These national and typological arrangements must not be confused with the promise of eternal salvation given to Abraham.
In The Marrow of Modern Divinity, Edward Fisher argues that God did not introduce a fundamentally different religion through Moses. The saving promise remained, although Israel received additional ordinances and ceremonies appropriate to that period of redemptive history.
This does not mean that the Abrahamic and Mosaic covenants were identical. Rather, the promise of salvation continued through the Mosaic economy while the law governed Israel’s national life and revealed God’s righteous demands, in a more distinct way.
The sacrifices, priesthood, and tabernacle also directed Israel beyond themselves to the promised Mediator, whose work these institutions anticipated (Heb 10:1–4).
Why Was the Law Given?
Paul explains that the law was added because of transgressions (Gal 3:19) and that its condemning function serves to stop every mouth before God (Rom 3:19–20). The law reveals the righteousness God requires while exposing the inability of fallen sinners to obtain righteousness through their own obedience.
In this sense, the law at Sinai expressed the demands of the covenant of works, requiring perfect obedience and pronouncing condemnation upon transgression. However, this does not mean that God reinstituted the covenant of works with Israel as another possible means of eternal salvation.
Rather, the law exposed Israel’s guilt and demonstrated the necessity of the promised Christ. As Paul explains, the law served as a schoolmaster to bring sinners to Christ, that they might be justified by faith (Gal 3:24).
The Mosaic economy contained both law and gospel, although they performed distinct functions. The law revealed sin and condemned self-righteousness, while the gospel promise directed sinners toward the righteousness provided in Christ.
Our Persistent Misuse of the Law
The irony is that sinners continually attempt to use the law to accomplish precisely what its condemning function demonstrates they cannot accomplish. Instead of recognizing their need for righteousness outside themselves, they attempt to establish their own righteousness through obedience.
Christians frequently repeat this mistake. Although we confess justification by faith alone, we often evaluate God’s acceptance according to our spiritual performance. Prayer, Scripture reading, church attendance, and obedience become measurements of our standing before God rather than expressions of faith in Christ.
The problem is not obedience itself, but employing obedience as the basis of God’s acceptance.
For the sinner seeking justification through works, the law requires an obedience he cannot provide. For the believer united to Christ, the moral law serves as a rule of life, directing the conduct of one who has already received life.
The distinction is between obeying to obtain life and obeying because life has already been given. Grace and obedience are not opposed; grace is opposed to obtaining acceptance through obedience.
For believers struggle with sin, repentance and mortification remain necessary, but they do not restore the favor of God, as though it was somehow lost through our disobedience. This is because our acceptance rests entirely upon Christ, in whom we have been made “accepted in the beloved” (Eph 1:6).
The law continues to expose our sin and direct our obedience, but it cannot become the foundation of our confidence before God.
The righteousness that the law demands is the righteousness Christ has provided, and our obedience proceeds from our acceptance in Him rather than any way to establish it.
