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 father of all who believe without being circumcised, so that righteousness would be counted to them as well,
And he gave him the covenant of circumcision. And so Abraham became the father of Isaac, and circumcised him on the eighth day, and Isaac became the father of Jacob, and Jacob of the twelve patriarchs.
Then David sent messengers to Ish-bosheth, Saul's son, saying, "Give me my wife Michal, for whom I paid the bridal price of a hundred foreskins of the Philistines."
If a stranger shall sojourn with you and would keep the Passover to the LORD, let all his males be circumcised. Then he may come near and keep it; he shall be as a native of the land. But no uncircumcised person shall eat of it.