Now the promises were made to Abraham and his descendant. It does not say, "and to your descendants," in the plural, but in the singular, "and to your descendant," that is, Christ.

And you are the descendants of the prophets and the heirs of the sacred compact which God made with your forefathers, when He said to Abraham: 'All the families of the earth are to be blessed through your posterity.' It was to you first that He sent His Servant, after raising Him from the dead, to bless you by causing every one of you to turn from his wicked ways."

And if you belong to Christ, then you are real descendants of Abraham, and heirs in accordance with the promise made to him.