Christ did this so that God's blessing promised to Abraham might come through Jesus Christ to those who are not Jews. Jesus died so that by our believing we could receive the Spirit that God promised.
Brothers and sisters, let us think in human terms: Even an agreement made between two persons is firm. After that agreement is accepted by both people, no one can stop it or add anything to it.
God made promises both to Abraham and to his descendant. God did not say, "and to your descendants." That would mean many people. But God said, "and to your descendant." That means only one person; that person is Christ.
This is what I mean: God had an agreement with Abraham and promised to keep it. The law, which came four hundred thirty years later, cannot change that agreement and so destroy God's promise to Abraham.
If the law could give us Abraham's blessing, then the promise would not be necessary. But that is not possible, because God freely gave his blessings to Abraham through the promise he had made.
So what was the law for? It was given to show that the wrong things people do are against God's will. And it continued until the special descendant, who had been promised, came. The law was given through angels who used Moses for a mediatorn to give the law to people.
But a mediator is not needed when there is only one side, and God is only one.
Does this mean that the law is against God's promises? Never! That would be true only if the law could make us right. But God did not give a law that can bring life.
Instead, the Scriptures showed that the whole world is bound by sin. This was so the promise would be given through faith to people who believe in Jesus Christ.
Before this faith came, we were all held prisoners by the law. We had no freedom until God showed us the way of faith that was coming.
In other words, the law was our guardian leading us to Christ so that we could be made right with God through faith.