So the law was our guardian until Christ came that we might be justified by faith

Galatians 3:15-4:7 

The promises were spoken to Abraham and to his seed. Scripture does not say “and to seeds,” meaning many people, but “and to your seed,”[meaning one person, who is Christ. What I mean is this: The law, introduced 430 years later, does not set aside the covenant previously established by God and thus do away with the promise. For if the inheritance depends on the law, then it no longer depends on the promise; but God in his grace gave it to Abraham through a promise.

The law was given through angels and entrusted to a mediator. A mediator, however, implies more than one party; but God is one.

Is the law, therefore, opposed to the promises of God? Absolutely not! For if a law had been given that could impart life, then righteousness would certainly have come by the law. But Scripture has locked up everything under the control of sin, so that what was promised, being given through faith in Jesus Christ, might be given to those who believe.

So the law was our guardian until Christ came that we might be justified by faith. Now that this faith has come, we are no longer under a guardian.

If you belong to Christ, then you are Abraham’s seed, and heirs according to the promise.

So you are no longer a slave, but God’s child; and since you are his child, God has made you also an heir.

Why?

Paul clearly described the relationship between the laws and the promise of the Lord to Abraham.

We were temporarily under the law as slaves, then we accepted Jesus Christ, and we can be released from slaves to sons of the Lord if we trust in Jesus.

How?

All of us are under the Law as slaves, until Christ came that we might be justified by faith; this is the good news to everyone. This is the Gospel in our churches and every Christian.