What, then, was the purpose of the Law? It was added in order to show what wrongdoing is, and it was meant to last until the coming of Abraham's descendant, to whom the promise was made. The Law was handed down by angels, with a man acting as a go-between.
But a go-between is not needed when only one person is involved; and God is one.
References for Galatians 3:20
Does this mean that the Law is against God's promises? No, not at all! For if human beings had received a law that could bring life, then everyone could be put right with God by obeying it.
But the scripture says that the whole world is under the power of sin; and so the gift which is promised on the basis of faith in Jesus Christ is given to those who believe.
But before the time for faith came, the Law kept us all locked up as prisoners until this coming faith should be revealed.
And so the Law was in charge of us until Christ came, in order that we might then be put right with God through faith.
Now that the time for faith is here, the Law is no longer in charge of us.