How reliable are promises? When God makes a promise, you can count on it! It won’t change. In Galatians 3:17–18 Paul contrasts two ways of salvation. The teachers in Galatia saw human efforts at keeping the law as the way to God’s favor. But Paul points you to the unshakeable promise of God.
God has made a gracious promise of salvation. God promised salvation to Abraham. God’s promise is unchangeable, v. 15. Paul begins with the concept of the covenant, an idea that is basic to Scripture. The Old Testament uses the word berith for covenant, a sovereign administration of law and grace. The New Testament term originally refers to a will, but also translates the Old Testament term. A human will, properly established is (or is supposed to be) unchangeable. How much more unchangeable is God’s covenant! That promise has its focus in Christ, v. 16. God made his covenant with Abraham. It included the land, an heir, and being a blessing to the nations, but the heart of it was to be a God to Abraham and his descendants. The God whose word is always truth underlines the certainty of his promise by taking an oath as he reassures Abraham of his covenantal faithfulness. The reference to Genesis 12:7 and the distinction between singular an plural stresses the authority and verbal accuracy of Scripture. “Seed” can be collective, but in this case it has its focus in one person, not just Issac, but ultimately on the Messiah, Jesus Christ. This promise is part of a covenant relationship, v. 17a, and thus it is permanent.
Keeping the law cannot provide the promised salvation. The law can only condemn. It expresses and reveals God’s will. It blesses conformity and obedience, v. 12. It condemns violation. The law convicts of sin, see v. 19. The law cannot give salvation. The law condemns the sinner. It cannot release from the bondage of sin, Romans 6:14. Be careful to understand Paul’s use of “law.” Paul is not an antinomian. He recognizes the permanent validity of God’s requirements, see 1 Corinthians 9:20,21. Here “law” refers to the whole Mosaic administration. It cannot provide salvation, not because it is faulty, but because we are sinners. Only grace can give salvation, v.18. What is earned is not a free gift. God’s promise is gracious. That is the point of v. 18. The law, which came 430 years after Abraham’s time, is not another way of inheriting God’s favor, alongside of or in place of God’s promise. “[I]t is the law which the heretical minds Paul is opposing in this letter are putting into competition with the promise — at bottom, in fact, they are placing it above the promise. It is by this opposition, this contrast, that the character of Paul’s conception of the covenant and the promise, yes, and of the law also, is entirely governed and determined. Law means demand, conditions; the promise, on the contrary, means free grant, guarantee, unconditionality.” (Herman N. Ridderbos, The Epistle of Paul to the Churches of Galatia, p. 135). Beware of thinking that when you have sinned, you somehow have to make up for it by good works.
When God gave the law he did not set aside the promise. The covenant promise was still valid under Moses. Salvation by works and by grace are utterly opposed. Paul contrasts them in absolute terms, Galatians 5:1; Romans 6:14. The Judaizers appealed to the law as a way of salvation. Thus Paul is forceful in v.1 8, see v. 21. The covenant with Abraham and that with Moses both required obedience. Obedience is clearly emphasized at Sinai. It was also required of Abraham, Genesis 17:1,9; 18:19. It is still required of you today. “Obedience as the appropriate and necessary expression of devotion to Christ does not find its place in a covenant of works or of merit but in a covenant that has its inception and end in pure grace.” (John Murray, Principles of Conduct, p. 200). Both covenants were gracious. The heart of the covenant is a relationship with God, Genesis 17:7. But that relationship was there in the Mosaic covenant as well, Exodus 6:7; 19:5,6; and therefore Leviticus 19:2. The history of redemption, the event of the Exodus itself, shows God’s grace. The law given at Sinai included the sacrificial system, pointing to the coming redeemer. The law does not annul or set aside God’s promises, v.17. The two dispensations or administrations are compatible (although they do have differences of emphasis). The two are not opposed, v. 21.
The law was added because of transgressions. The law was added until the promised Seed should appear. It has the character of an appendix, a supplement. It shows sin for what it is. It makes clear the need for a Savior. The law points to Christ. It is not the issuance of an administration of salvation by works. God’s law continues to point believers to the perfect Savior.
Come to God through your perfect Mediator. Angels were active in giving the law, Hebrews 2:2; Acts 7:53. Just how they were involved, the Bible does not tell us. Moses was a mediator between God and the people. There is an implied contrast with the directness of Abraham’s relationship with God. But your access to the one God is even more direct, for you come directly through Christ. You have the perfect mediator, the one who is both God and man. He represents you prefectly. Thus the law cannot replace promise as a way of inheritance. Salvation is by grace alone.
In all of redemptive history the grace of God in Christ is evident. Promise, at least the promise of God, cannot be set aside. God’s covenant is unchangeable. Jesus Christ is the only way of salvation.