Phil. 3:2-4 - Beware

2 Beware of the dogs, beware of the evil workers, beware of the false circumcision;
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,
4 although I myself might have confidence even in the flesh. If anyone else has a mind to put confidence in the flesh, I far more:

Put No Confidence in the Flesh

Vs. 2 - “Beware of the dogs” - We are thinking, “Awww. That’s not a nice thing to say about pets.” In those times, in that area, dogs were not pets. Dogs were mostly feral, running in packs, and were scavengers. The dogs ate dead things, dead bodies and therefore were unclean. One famous incident concerned King Arab and Jezebel (a truly evil king and queen). She was killed and her body was thrown off the wall of the city. They went out later to get her and bury her (she had been queen, after all), and all they found was her skull - the dogs had picked her clean! (See: 1 Kings 14:11; 16:4; 21;23; 2 Ki. 9:33-35). The Jews treated Gentiles like they were dogs. This may be part of the reason they could see no reason to share the gospel with Gentiles - why waste this message on dogs, on the unclean? (See: Matt. 15:26).
Paul draws on that imagery. False teachers are unclean in Paul’s estimation - no better than the carrion eating dogs. Following false teachers prevents you from joyfully following Christ, just as being unclean meant you could not come into the temple and do sacrifices.
We are to be pure, just as Christ is pure. Christ and Christ alone provides that purity, (See: Jude 24). His blood purifies us of all sin. (1 John 1:7) 

“beware of the false circumcision” - This is the first mention of the problem they are facing. The first and second chapters are reminding them of their salvation and joy, of Paul’s love and concern for them. This warning is not as severe as that given in the letter to the Galatians.
Circumcision is similar to Christian baptism in that it is a physical announcement, or symbol to the world that you belong to God and Jesus. Circumcision did not save the Jew, but it showed the world their life was committed to God. Baptism does not save. Being baptized tells the world you have made a commitment to Christ as your Lord and Savior. It is faith in Christ, His sacrifice and resurrection, that will give you the inheritance of eternal life.
Adding circumcision to the requirements to be ‘saved’ will NOT save you from your sins. This means false hopes. Basing your life on false information takes you further away from certainty and hope.

Vs. 3 - “We are the true circumcision” - What is Paul writing about, “True circumcision?” Physical circumcision has no impact on your salvation, just as it did not save the Jews. It is therefore “false” if you place your hopes on it.
So, what is “true circumcision?” Paul addresses the effectiveness of circumcision in Rom. 2:25-29. The outward evidence is of little value if the inner quality of the man is not centered on Christ. He reminds us that Abraham’s righteousness was accorded him before Abraham was circumcised. His faith that was rewarded. (See: Rom. 4:10-12.)
Our bodies are dead to eternity. We are literally “The Walking Dead.” God does not repair these bodies, but provides us with new bodies that will be just like Jesus. - we will be just as He is. (1 John 3:1-3) The flesh, the old nature, means death. (Rom. 8:10, 13; 1 Cor. 15:42; 1 Pet. 1:15) Living in the Spirit means life. (2 Cor. 3:16) The difference between the flesh and the Spirit is that of death and life. (See: Rom. 7:5, 8:6,13; 1 Pet. 3:18) Compare Rom. 7:4 with Rom. 8:13.

“Worship in the Spirit of God...” - Christ said, “But an hour is coming, and now is, when the true worshipers will worship the Father in spirit and truth; for such people the Father seeks to be His worshipers. God is spirit, and those who worship Him must worship in spirit and truth." (John 4:23-24) The Jews gloried in their relation with Abraham - they were his ‘children’, and so by extension they were ‘children of God’ because of the promise made to Abraham. The personal physical evidence of that was circumcision. Apparently no other nation or tribe did this. The Jews were unique in this matter.
However, this claim has no more validity than a person claiming they are ‘Catholic’ because they are born to Catholic parents. Each person is responsible for their own decisions. (See Ezek. 18:20)
What is the key to being the ‘true circumcision”? Jesus said,”If you abide in My word, then truly you are disciples of Mine; and you shall know the truth, and the truth will make you free.” See Rom. 10:9,10; Acts 16:31. His word: confess that “You are the Christ, the Son of the Living God.” (Matt. 16:15). Love God. Love others - just as God in Christ has loved you.

Vs. 4 - “might have confidence in the flesh.” - In verse three above, Paul puts “no confidence in the flesh.” He says that if anyone, anywhere, anytime could be confident in personal performance and accomplishments, it would be Paul. If anyone is going to boast, it would be him. (See: 2 Cor. 11:18) He explains in the next two verses.

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