Sermon by St. Ambrose the Bishop
So the Child is circumcised. This is the Child of whom it is said: Unto us a Child is born, unto us a Son is given: or again: Made under the Law to redeem them that were under the Law: or again: To present him to the Lord. In my commentary on Isaiah I have already explained what is meant by being presented to the Lord in Jerusalem, and therefore I will not enter into the subject again. He that is circumcised in heart gaineth the protection of God, as it is written: The eyes of the Lord are over the righteous. Ye will see that as all the ceremonies of the Old Law were types of realities in the New Law, so the circumcision of the body signified the cleansing of the heart from the guilt of sin.
But since the body and mind of man remain yet infected with a proneness to sin, the circumcision of the eighth day is meant to put us in mind of that complete cleansing from sin which we shall have at the resurrection. This is doubtless to be inferred from the words: Every male that openeth the womb shall be called holy unto the Lord. That is, these words are literally true only of the delivery of the Blessed Virgin. Verily, he that opened her womb was holy, for he was altogether without spot. And we may gather that the Law hath this meaning because the Angel said almost the same words: That Holy Thing which shall be born of thee shall be called the Son of God.