Moreover, we learn from the Scripture itself, that God gave circumcision, not as the completer of righteousness, but as a sign, that the race of Abraham might continue recognizable. For it declares: “God said unto Abraham, Every male among you shall be circumcised; and you shall circumcise the flesh of your foreskins, as a token of the covenant between Me and you.” (Gen 17:9-11) This same does Ezekiel the prophet say with regard to the Sabbaths: “Also I gave them My Sabbaths, to be a sign between Me and them, that they might know that I am the Lord, that sanctify them.” (Ez 20:12) And in Exodus, God says to Moses: “And you shall observe My Sabbaths; for it shall be a sign between Me and you for your generations.” (Ex 21:13) These things, then, were given for a sign; but the signs were not unsymbolical, that is, neither unmeaning nor to no purpose, inasmuch as they were given by a wise Artist; but the circumcision after the flesh typified that after the Spirit. For “we,” says the apostle, “have been circumcised with the circumcision made without hands.” (Col 2:11) And the prophet declares, “Circumcise the hardness of your heart.” — Book IV, Chapter 16