Philippians 3:2-7 (New International Version)
2Watch out for those dogs, those men who do evil, those mutilators of the flesh. 3For it is we who are the circumcision, we who worship by the Spirit of God, who glory in Christ Jesus, and who put no confidence in the flesh— 4though I myself have reasons for such confidence. If anyone else thinks he has reasons to put confidence in the flesh, I have more:
5circumcised on the eighth day, of the people of Israel, of the tribe of Benjamin, a Hebrew of Hebrews; in regard to the law, a Pharisee; 6as for zeal, persecuting the church; as for legalistic righteousness, faultless.
7But whatever was to my profit I now consider loss for the sake of Christ.
These days when you ask someone whether or not they think they will go to heaven when they die, you often get answers like,"Sure!I go to church occasionally and I'm a good person.", "I'm not that bad...I'm better than that other guy!", or "If my good outweighs my bad, I think I will!". The answer to this question are as varied as the people who are asked. The problem is that in today's world, people have too much "Self-Confidence" when it comes their salvation.
Not that self-confidence in many things is wrong, but in terms of whether or not we will spend eternity with God, we can't make it with our own efforts. If you take time to study the wisdom of the Bible, you will began to discover that the Old Testament God reveals His divine Law and points to a future Messiah that will rescue us from mankinds in-ability to keep the Law, while the New Testament reveals the Messiah as Jesus Christ as the one who accomplishes the Law.
The Law(The Ten Commandments or the Mosaic Law)acts as a mirror, in which we look at ourselves to see whether or not we measure up to God's standards. How many of us have looked at another with lust? Yet, Jesus in Matthew 5:28 tells us that if we do, we have committed adultrey. And how many have taken something that didn't belong to us, no matter how small and insignificant? Yet, that very act makes us guilty of stealing. Even looking at the guy across the street and being jealous of his new Porsche makes us guilty of coveting!
When we realize that as human beings we cannot get by without breaking God's Law, we should discover that we are hopelessly lost, because one single act of breaking God's Law makes us guilty of them all and condemns us to separation from God for eternity (damnation). It is not pleasant to read, and many of us just ignore it thinking that it will go away, but the truth is that someday we will stand before the judgement of God which will determine our eternal existence.
That is what Paul was pointing out in the verses in Philippians above. There were Jews that were persecuting new gentile(the common, non-Jewish person)Christians, because they were not following certain rules and regulations that had been imposed on the Jewish people. Paul was making a point that we can place no confidence in man's laws, rules and regulations for salvation.
In fact after the Law was given to the Jewish people, they went on to list 613 commandments in the Torah, and added to that additional traditions for Jewish living in the Mishnah, the halakhic Midrash, and the Talmud. But it is not only the Jewish religion, in fact every other religion out there require works on our own behalf to have a hope of salvation(ask any Mormon, Jehovah's Witness, Muslim, etc. how they know whether or not they are saved). It is only because of the shed blood of Jesus Christ, God in the flesh, on the cross as the payment for our sins before a Holy God, that we have the assurance of being "saved".
I do not rely on my own "self", but I place my "confidence" of salvation in Jesus and Jesus Christ alone. Paul says it best, and it is easiest to understand in the New Century Version of the continuation of the text above:
8 Not only those things, but I think that all things are worth nothing compared with the greatness of knowing Christ Jesus my Lord. Because of him, I have lost all those things, and now I know they are worthless trash. This allows me to have Christ9 and to belong to him. Now I am right with God, not because I followed the law, but because I believed in Christ. God uses my faith to make me right with him.10 I want to know Christ and the power that raised him from the dead. I want to share in his sufferings and become like him in his death.11 Then I have hope that I myself will be raised from the dead. Philippians 3:8-11 (New Century Version)