Beware of dogs, beware of evil workers, beware of the concision.
Note 5 at Php 3:2: The New Testament uses the word "dog" in both a natural and metaphorical sense. The Jews used this term when describing Gentiles, with the idea of them being ceremonially impure and sinful. In the Old Testament, the Lord used this term to refer to a male prostitute (De 23:18, compare with New International Version).
Note 6 at Php 3:2: Circumcision was the dominant action and sign of the Old Covenant that God made with Abraham (Ge 17:10-11). The legalistic Jews had lost the significance of the sign and were blindly observing the action, believing that circumcision itself produced salvation. Therefore, the issue of circumcision symbolized the difference between the Old Testament and the New Testament means of salvation (see note 2 at Ac 15:1).
Here, Paul used a play on the word "circumcision" by using the word "concision," which means "mutilation" (Strong's Concordance). Circumcision, done the way the legalistic Jews did it (i.e., in order to obtain salvation), was nothing more than mutilation. It had no saving power whatsoever. In fact, it had a similar effect as castration. It stopped the regenerating power of the Holy Ghost in an individual's life. These Jews were mutilating men spiritually by adding legalistic rules to Christ's Gospel.