The Function of the Law. Galatians 3:15-22 What is the purpose of the law if justification is by faith? It doesn’t add to or cancel out justification by faith, but it highlights our sins and causes us to face the consequences of sin. It does not oppose God’s promises but prepares us to receive what only God can give. Humans cannot alter a covenant or contract with God once it has been ratified.
Abraham's seed refers to our Lord Jesus Christ and those who have placed their faith in Him. He fulfilled the terms of the covenant God made with Abraham. He is the focus of God’s promises. Four hundred thirty years before the law was given by the Lord to Moses on Mount Sinai, God spoke to Abraham and made him a promise that He would make of him a great nation. This wasn't because Abraham was some special, extraordinary person, but because the Sovereign God knew that Abraham was willing to see and believe by faith. When he heard God's voice, he obeyed what God had said. He believed in God.
He didn't follow a set of laws or have the Ten Commandments guiding his life. He didn't need them because he had God. Abraham acted on what God said, forming a covenant not to produce faith, but because faith was demonstrated through action. That is what God expects from us. Jesus' death on the cross, as the full payment for our sins, is God's gift of salvation. God has promised to save us when we trust in Christ, believing His word is how we hear His voice and accept Him. This is the foundation of the Gospel and the core of Christianity. It’s not about faith plus other things. Salvation is God's grace alone—planned, accomplished, and secured by Him—and nothing can change that. There’s no reason to believe we need to add anything to that divine gift.
Why did God give the law? What’s the point in having rules if they are impossible to follow? The law helps us understand God's standard of behavior. It shows us how God expects us to live and reveals His will. On the positive side, it also highlights human sin and how we cannot reach that standard on our own. A wall might look perfectly upright at first, but the truth is shown when a plumb line is hung next to it. The law is like that plumb line. Some people have bad habits they’ve grown used to, but they can't be considered wrong unless there is authority stating otherwise. That authority is the law. It’s based on unchanging principles of divine holiness, which serve as the foundation for acceptable conduct.
The "one seed" was the common source of life given to Abraham in the form of a covenant. Simply believe in God. The law does not have that authority; it merely tells us what will happen when we don't believe in God. It also highlights the reasons why we should believe in Him. That law is written on the heart of every human being. The moral laws and ceremonial laws of the Jews were given in written form. The seed of promise was made long before that, indicating that faith is how one comes to God. "Without faith, it is impossible to please God. For he that cometh to God, must believe that He is, and he is a rewarder of them that diligently seek Him."
The law needed a mediator, and that mediator was Moses. Faith doesn't require a mediator. The role of a mediator is to unite two opposing sides. The one seed established the fact that our covenant with God is based on faith—personal faith in a living, personal, all-knowing God who is my Father. The inheritance of justification and the gift of the Holy Spirit come from believing God's promise, not from law-keeping. God's grace justifies us and grants us life. The law condemns us and, through its righteous justice, kills us. It reveals how great our transgressions are.
The purpose of the law of Moses was a temporary definition of righteousness passed down through the mediation of angels and Moses, not to justify us. It clarified sin until our Lord Jesus Christ came into the world. The "One Seed," our Lord Jesus Christ, has been revealed and God's grace freely given, not because of anything we have or could do, but because of God's promise alone. The law does not oppose God's promises but highlights men's failure.
When sin is defined this way, we remain enslaved to it. Everyone is under its control, and nothing the law can do can free us. The law acted as a guard to keep people from following the common practices of neighboring cultures around God's people. In that sense, it was good for separating what is of God from what is worldly. But to achieve justice, its demands had to be met. That is what Jesus accomplished for us.
The law was given through Moses as a mediator and, therefore, does not have the same impact as the promise of God, which He gave directly to Abraham. God is the God of both Jews and Gentiles, and both are united through the Gospel. The law does not oppose God's promises, but it cannot fulfill them. The relationship between the law and God's promises is that of need (the law) and fulfillment (the promises). God did not design the law to give eternal life or to make us righteous. Instead, it reveals our need for life, which we receive as a gift through faith in our Lord Jesus Christ.
Faith has a personal, real object that has been revealed to the world—a Living Savior. He is the One whose "day" Abraham saw and "was glad" because of that promise. By faith, it was as good as already done. The salvation message, the reality of salvation through the substitution of an innocent victim, was personal to Abraham. To us, the law is our teacher, like a child trainer, to teach us that there is a principle of faith by which we live. The law teaches us morals, respect for authority, and manners that are acceptable for living in an orderly society. The "child trainer" has the right to show what is right and to punish the wrongdoer.
The scripture (the law) clearly defines what sin is and shows our need for the Lord Jesus Christ as our Savior from sin. We are trapped by sin like prisoners, and the only way to be released is to trust in the promise of faith in our Lord Jesus Christ. The law acts like a prison guard. It also functions like a strict tutor who disciplines a young child harshly to help them behave.