T. David Gordon notes that one Abrahamic promise (land and offspring) was fulfilled in the Old Covenant, while the other promise about one individual seed blessing all nations was fulfilled in the New Covenant.
Paul understood the covenant with Abraham to include essentially three promises: That God would give Abraham numerous descendants (“seed”), that God would give Abraham (and his seed) the land of Canaan, and that God would bless all the nations of the world through Abraham and his seed. Plainly enough, the Israelites became numerous during their four hundred years in Egypt, and equally plainly, through Joshua and the judges, they inherited the land of Canaan. But they did not become the means by which all the nations/Gentiles were blessed until the calling of Paul…
[T]he “Seed” would come through whom the promise would be fulfilled and the nations would be blessed (3:19). Paul identified the “Seed” as Christ (3:16), and argued that the nations are indeed now being blessed by that Seed of Abraham, and that therefore, the temporary covenant made only with Abraham’s descendants must become obsolete and disappear…
[O]ne might argue that Paul perceived the New Covenant realities in Christ as bringing the final third of the Abrahamic promise to fruition
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