Romans 4:11 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:

Genesis 17:11 And ye shall circumcise the flesh of your foreskin; and it shall be a token of the covenant betwixt me and you.