Romans 4:11-12

4:11 And he received the sign of circumcision as a seal of the righteousness that he had by faith while he was still uncircumcised, so that he would become the father of all those who believe but have never been circumcised, that they too could have righteousness credited to them. 4:12 And he is also the father of the circumcised, who are not only circumcised, but who also walk in the footsteps of the faith that our father Abraham possessed when he was still uncircumcised.

Romans 4:16

4:16 For this reason it is by faith so that it may be by grace, with the result that the promise may be certain to all the descendants – not only to those who are under the law, but also to those who have the faith of Abraham, who is the father of us all