As Abraham believed God, and it was accounted to him for righteousness:

so ye know that they who believe, are the children of Abraham.

And the scripture foreseeing that God would justify the gentiles through faith, preached the gospel to Abraham long ago, saying, "In thee shall all nations be blessed."

So then they that believe, are blessed with believing Abraham.

that the blessing of Abraham might come on the gentiles by Christ Jesus; that we through faith might receive the promise of the Spirit.

Now the promises were made to Abraham, and to his seed. He doth not say, "and to seeds," as of many; but as of one, "and to thy seed," which is Christ.

For if the inheritance be from the law, it is no more from the promise: whereas God gave it to Abraham by promise.

And if ye be Christ's, then are ye Abraham's seed, and heirs according to the promise.

where it is written, that Abraham had two sons, one by a servant, and one by a free-woman?