Therefore no one will be declared righteous in his sight by observing the law; rather, through the law we become conscious of sin. But now a righteousness from God, apart from law, has been made known, to which the Law and the Prophets testify. Romans 3:20-21
The purpose of the law was to make us conscious of sin. God knew we would never be able to keep the law, but we didn’t. Throughout the Old Testament, we see the Israelites attempting to keep the law and how miserably they failed. Even the Jews who were working hard to keep the law in Jesus and Paul’s time failed miserably too. Paul wrote about their failures and concluded, “As it is written: ‘God’s name is blasphemed among the Gentiles because of you’” (Romans 2:21-24).
The purpose of the law is to show us that we need a Saviour. We can’t achieve God’s standards of holiness by our own efforts. The law leads us to Christ. Paul writes, “So the law was put in charge to lead us to Christ that we might be justified by faith” (Galatians 3:24). Christ was the only one who was able to keep the law and we are made righteous by being “in him.” This was always part of God’s plan which is why “the Law and the Prophets testify” to it.
Once we have found our righteousness in Christ through faith, we continue the way we began. Paul asks the Galatians “Did you receive the Spirit by observing the law, or by believing what you heard?” (Galatians 3:2). We received the Spirit by believing so we continue to live by faith. We don’t rely on observing the law for our justification because we know we simply can’t do it.