Galatians 3:17-21

What I am saying is this: the Law, which came 430 years later, does not invalidate a covenant previously ratified by God, so as to nullify the promise.

For if the inheritance is based on law, it is no longer based on a promise; but God has granted it to Abraham by means of a promise.

Why the Law then? It was added on account of the violations, having been ordered through angels at the hand of a mediator, until the Seed would come to whom the promise had been made.

Now a mediator is not for one party only; but God is only one.

Is the Law then contrary to the promises of God? Far from it! For if a law had been given that was able to impart life, then righteousness would indeed have been based on law.