You can’t understand the purpose of the Ten Commandments until you grasp the timeline of when Moses climbed the mountain to receive them.
God gave the 10 Commandments to Moses in Exodus 20. In Exodus 14, the Israelites are walking through the Red Sea on dry ground. Why did God give the Law after this event? It would seem that God should have given the Law, and based on how good they adhered to it, he would have rescued them from Egypt. That’s not how he did it.
He rescued and redeemed a people for his own, then he gave them rules to live by. Here’s the essential point:
We don’t keep the Law in order to be God’s people, we keep the Law because we are his people.
19 Why the law then? It was added because of transgressions until the Seed to whom the promise was made would come. The law was ordered through angels by means of a mediator. 20 Now a mediator is not for just one person, but God is one. 21 Is the law therefore contrary to God’s promises? Absolutely not! For if a law had been given that was able to give life, then righteousness would certainly be by the law. 22 But the Scripture has imprisoned everything under sin’s power, so that the promise by faith in Jesus Christ might be given to those who believe. 23 Before this faith came, we were confined under the law, imprisoned until the coming faith was revealed. 24 The law, then, was our guardian until Christ, so that we could be justified by faith. 25 But since that faith has come, we are no longer under a guardian, 26 for you are all sons of God through faith in Christ Jesus (Galatians 3:19-26, HCSB).
In this passage, Paul lays out a pivotal argument for Christians to understand. So many people think that before Christ, everyone had to keep the Law to experience salvation. What many don’t understand is that God gave the Law not so that everyone had to keep it but to show the impossible nature for one to keep it.
The Law was given as a measuring stick. The bar was raised so high that no one except for Jesus could keep it, and that was the whole point. So when Paul wrote that the law “was our guardian” (v. 24), he is revealing that God’s rules have a way to guide us and watch over us. They keep us in line, and they also make us long for a way around that standard. The Law reveals our sinfulness. It shows us how desperate we are for a Savior.
And then Jesus came.
Precious and unmistakable grace burst onto the earth when God became man.
And through faith in Christ Jesus, we are sons of God (v. 26). Grace wasn’t God’s plan “B.” He never had to regroup when the whole Law thing never panned out.
His plan from the beginning was to give us a standard that we could not keep, so that he could send his son to keep it himself and offer salvation to the world.