Galatians 3:15. “Brethren, I speak after the manner of men: Though it be but a man’s covenant, yet if it be confirmed, no man disannulleth, or addeth thereto.”
Paul says in this verse that he is speaking of civil transactions or contracts like those made between men. When such an agreement is signed, sealed, witnessed, and duly recorded, it stands under the protection of the civil law, and nothing can be legally added to or taken from it.
So it is with the Abrahamic covenant and promises, made 420 years before the law. The law of Moses cannot make those promises of no effect. Inheritance is not of the law, but of the promise of the Abrahamic covenant.
The word disannul had me puzzled. It seems similar to unthaw, which is a contradiction in terms. So I looked it up. It’s one of those weird things about English, I guess, because annul and disannul mean the same thing. So, in case you were wondering too, I hope that clears things up for you 🙂