Philippians 3:1-5
Phil 3:1 (KJB)
Finally, my brethren, rejoice in the Lord. To write the same things to you, to me indeed is not grievous, but for you it is safe.
Finally - For the rest or remaining
Grievous - Troublesome or irksome (boring, tedious)
Here the Apostle Paul is not stating that he is finishing his letter just yet but is stating to the Philippians that in the remaining portion he is going to be exposing the false teachings which may affect them. He instills in them that they are to rejoice in the Lord because our rejoicing is rooted in Christ through the fruit of the Holy Spirit. Paul is telling them that he does not find it tedious to write the same things he has already written to them previously. He considers this repetition to be a safe precautionary measure to ensure that the Philippians are well grounded in the faith. This is the principle we use generally in Christianity that we read and study the Bible repetitively because even though the words are the same, the Holy Spirit opens our eyes to something new which we never saw before. The Bible is a living book because its author is the living God. I have been saved for 28 years at the time of this writing and the Lord still opens my eyes to new things in Scripture.
Phil 3:2 (KJB)
Beware of dogs, beware of evil workers, beware of the concision.
Beware - Notice or watch out for
Concision - Mutilated
Paul is giving a three-fold warning in this verse. First, he warns of the dogs. He uses the term “dogs” because dogs were unclean and in this case it is a metaphor for being unsaved. The dogs of Palestine would also be in packs where they would roam the streets and cause problems. They also attacked people on occasion. He is calling those who bring false Gospels dogs because they prey on unsuspecting people and when they believe they have an audience, they pounce on them with the false teachings. Then he warns about the evil workers. These are the same ones who oppose the truth of the Gospel and would attempt to either bring the Philippians under the law or would bring them under the spell of a false gospel. Then he speaks of them as being the concision. This is an interesting description because he is warning the Philippians against those who are the mutilated circumcision versus the true circumcision. These false teachers claimed to be the true circumcision but as Paul defines them, they are only a mutilated or false copy of the true salvation. This may also be alluding to the practice of mutilating the body which was practiced by many false religions. (1 Ki 18:28 KJV) And they cried aloud, and cut themselves after their manner with knives and lancets, till the blood gushed out upon them. Paul warned the Philippians to be on the alert for these type of false teachers and you will know them by their teachings and actions.
Phil 3:3 (KJB)
For we are the circumcision, which worship God in the spirit, and rejoice in Christ Jesus, and have no confidence in the flesh.
Confidence - Satisfaction, persuasion, or influence
Here is one of the most revealing verses in Scripture concerning the Christian. Normally circumcision is attributed to Israel but here Paul is giving a new definition of it. (Deu 10:16 KJV) Circumcise therefore the foreskin of your heart, and be no more stiffnecked. As far back as Deuteronomy, we read about circumcising the foreskin of the heart and that is an allusion to salvation by grace, which Moses was a recipient of. This means that salvation did not come through physical circumcision but came through the circumcision of the heart. Now back to Philippians 3:3 where Paul now states that the Christian is the circumcision and the result is that we worship God in the spirit, whereas Israel had worshipped under the Mosaic law and that was according to the strictures of the law. Those under grace are the only ones who worship God in the Spirit. (John 4:24 KJV) God is a Spirit: and they that worship him must worship him in spirit and in truth. Those who do not possess the Spirit of God will be unable to worship Him because they are unsaved AKA spiritually dead.
Another aspect of this verse which is important is that Paul is changing the meaning of “circumcision.” He is now calling the believers “THE circumcision.” Notice the definite article “the” which means there are no others. Just because one still practices physical circumcision does not mean that God recognizes it. The age of law is over because it was fulfilled in Christ. The only circumcision that God now recognizes is that of spiritual circumcision which is salvation by grace. Paul is now referring to Christians as spiritual Israel. There are other verses which confirm this.
Paul states that a true Jew is one who is born again of the Spirit of God under the eternal covenant of Grace in contrast to the covenant that Israel made with God at Mt. Sinai which they could not keep. Only Christ was able to fulfill every demand of God’s righteous law and those who are in Christ, are as those who had kept the law in its entirety and perfectly. Thusly because of Christ’s sacrifice, we are now members of Spiritual Israel or the Israel of God. This is borne out in quite a number of other verses.

(Rom 2:28-29 KJV) For he is not a Jew, which is one outwardly; neither is that circumcision, which is outward in the flesh: {29} But he is a Jew, which is one inwardly; and circumcision is that of the heart, in the spirit, and not in the letter; whose praise is not of men, but of God.

(Deu 30:6 KJV) And the LORD thy God will circumcise thine heart, and the heart of thy seed, to love the LORD thy God with all thine heart, and with all thy soul, that thou mayest live.

(Isa 45:17 KJV) But Israel shall be saved in the LORD with an everlasting salvation: ye shall not be ashamed nor confounded world without end.

(Rom 9:6 KJV) Not as though the word of God hath taken none effect. For they are not all Israel, which are of Israel:

(Gal 3:7 KJV) Know ye therefore that they which are of faith, the same are the children of Abraham.

(Gal 3:16 KJV) Now to Abraham and his seed were the promises made. He saith not, And to seeds, as of many; but as of one, And to thy seed, which is Christ.

(Gal 6:16 KJV) And as many as walk according to this rule, peace be on them, and mercy, and upon the Israel of God.

(Eph 2:12 KJV) That at that time ye were without Christ, being aliens from the commonwealth of Israel, and strangers from the covenants of promise, having no hope, and without God in the world:

Every verse in this list speaks of the eternal covenant of Grace which comes only through the Lord Jesus Christ. This is the eternal Israel which God speaks of in Isaiah 45:17. The true Jew is the one who is saved through the Lord Jesus Christ, who was of the tribe of Judah. Those who are of the physical tribe of Judah who boast in their circumcision are as those who are uncircumcised, or unsaved. Those who are in the Lord Jesus Christ are of the spiritual tribe of Judah, which is the eternal Israel or the true Jew who is circumcised in the heart. This is why Paul states that the true Christian has no confidence in the flesh because it has no ability to save. Only those who are generated in the Spirit are saved.
Phil 3:4 (KJB)
Though I might also have confidence in the flesh. If any other man thinketh that he hath whereof he might trust in the flesh, I more:
Confidence - Trust
In verses 4-6 Paul is now giving a list of his accomplishments before salvation. He did not do this to boast about what a good Jew he was but he did it to show the folly of trying to become right with God through the flesh and the law. This principle can also be applied to those in false ministries or churches who believe that they can become saved by following a prescribed list of works. There is no one who will become saved by human merit. We become saved only through the grace given by the Lord Jesus Christ. (John 10:27-28 KJV) My sheep hear my voice, and I know them, and they follow me: {28} And I give unto them eternal life; and they shall never perish, neither shall any man pluck them out of my hand. Paul wanted to show the Jews that it was useless to continue obeying the law when the law was fulfilled in Christ and now salvation by grace has supplanted the keeping of the law (although anyone who became saved before the cross was still saved by grace without the keeping of the law).
Phil 3:5 (KJB)
Circumcised the eighth day, of the stock of Israel, of the tribe of Benjamin, an Hebrew of the Hebrews; as touching the law, a Pharisee;
Stock - Race or offspring
Here Paul shares some of his accomplishments. First, he states that he was circumcised on the eighth day according to the law. (Lev 12:3 KJV) And in the eighth day the flesh of his foreskin shall be circumcised. God gave the eight day for circumcision because that is when the clotting factor in the blood forms. If a person would be circumcised on the seventh day, they could bleed out and die. He then states that he was of the stock of Israel which reveals that he was not adulterated with any other nation in his lineage. He was of the tribe of Benjamin and Benjamin had been faithful to the tribe of Judah when the other ten tribes were not. (1 Ki 12:21 KJV) And when Rehoboam was come to Jerusalem, he assembled all the house of Judah, with the tribe of Benjamin, an hundred and fourscore thousand chosen men, which were warriors, to fight against the house of Israel, to bring the kingdom again to Rehoboam the son of Solomon. Hebrew of the Hebrews which means that he was raised in a home which spoke Hebrew because many of the Jewish homes had spoken Greek and also followed Greek customs. So Paul is distancing himself from those who chose to amalgamate with the pagan societies and their philosophies. This is why he was probably so zealous for the law and against Christians because he saw it as another sect which would further amalgamate the people of Israel with false religion. He was a Pharisee which was the strictest of the religious groups of his day and was very hostile to the Lord Jesus Christ and afterwards Christians, as evidenced by himself who oversaw the stoning of Stephen.