Rom 4.11-16 And he received the sign of circumcision, a seal of the righteousness of the faith which he had yet being uncircumcised: that he might be the father of all them that believe, though they be not circumcised; that righteousness might be imputed unto them also:
Gal 3.29 And if ye be Christ's, then are ye Abraham's seed, and heirs according to the promise.