He received the sign of circumcision as a seal of the righteousness that he had by faith while he was still uncircumcised. The purpose was to make him the ancestor of all who believe without being circumcised and who thus have righteousness reckoned to them,
For the scripture says to Pharaoh, “I have raised you up for this very purpose, that I may show my power in you and that my name may be proclaimed in all the earth.”