WPNT(i)
15 Brothers: as a man I speak a covenant; though only of a man, once it has been ratified no one annuls or adds to it.
16 But to Abraham were spoken the promises, and to his Seed. He doesn’t say “and to seeds”, as about many, but “and to your seed”, as about one, who is Christ.
17 Further, I say this: a covenant confirmed beforehand by God in Christ cannot be annulled by the law that came four hundred and thirty years later, so as to make the promise of no effect.