This is a subsidiary post of Jew.
Subsidiary post: Old Testament References to Jews Which Can Be Applied Spiritually
Prior to Christ, being a Jew was something determined according to the flesh. That is, were you a descendant of Abraham, Isaac, and Jacob. However, in bringing in the kingdom of God, Jesus transformed this designation into something spiritual. The following verses speak to this change from flesh to spirit in what it means to be a Jew.
Acts 7:51 – Note that Stephen is addressing these words to a largely Jewish audience. Thus he is telling them that while they may be circumcised in the flesh, they are not so spiritually speaking. In the new age of Jesus Christ, this emphasis on spiritual over physical has become paramount.
Philippians 3:2 – “Beware of the dogs, beware of the evil workers, beware of the false circumcision;” – NASB marginal note says that “”false circumcision” is literally “mutilation” (Greek = katatome)
Philippians 3:3 – “for we are the true circumcision, who worship in the Spirit of God and glory in Christ Jesus and put no confidence in the flesh,” – The word “true” is an insertion by the translator for the sake of clarity; NASB marginal note shows that the Greek for “circumcision” is “peritome,” and thus to be contrasted with “katatome” in the previous verse.