Galatians 3:16-20

Now the promises were spoken to Abraham and to his seed. He does not say, “And to seeds,” as one would in referring to many, but rather as in referring to one, “And to your seed,” that is, Christ.

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.