Paul is most likely still addressing Peter and the other Jews who were acting unfaithfully. This flows smoothly from what Paul said to Peter "before them all" (verse 14), and it is not until the beginning of chapter 3 that Paul directly addresses the Galatians again.
They were Jews by nature, or by birth, as opposed to the Gentiles, who were, by definition, of a different race. Paul does not mean that one race was inherently righteous and the other was inherently sinful. However, the Greek word used here for "sinners" is hamartoolos, which often signifies a pagan, one who had no knowledge of the true God. This is not a condemnation of Gentiles in general, but rather a statement that they had no connection with God by heritage as the Jews did. Romans 14:3 states the principle that whatever is not of faith is sin, so anyone not knowing God—and thus not having faith in Him—would be a "sinner." To show further that Paul is not playing favorites, Romans 3:9 shows that both groups of people (Jew and Gentile) were sinners in terms of coming short of the glory of God and breaking His law.
David C. Grabbe
Verse 15 declares that being born an Israelite indicates a privileged birth. The privilege results from being part of the Old Covenant nation, thus having direct contact with God's Word, which contains His promises and instructions. This provides the possibility of faith because faith comes from hearing God's Word (Romans 10:17).
However, even having that privilege is of itself no benefit regarding justification. Why? Because a person is justified only through faith in Jesus Christ. Through this means and this means only, a person is declared righteous or innocent of sin. Thus, if one does not take advantage of its availability, the availability itself is of no value. Faith in Jesus Christ and His message is what is important about this way of life.
Paul makes a definitive statement regarding obedience following justification by faith in verses 17-18. The thing that he destroyed through faith and repentance was his former way of life with its mountain of sin accumulated during his unconverted life before justification. Paul was determined not to return to that sinful way. To do this, he had to live to God (verse 19), that is, to obey God's laws so that he would not sin and therefore bring to naught his justification through Christ's sacrifice. He is clearly stating that keeping God's laws is required, even though keeping them does not earn salvation.
We need to make sure that we understand this important reality: Being justified is a major step toward salvation, but this does not mean that the person's character is now fully changed. It means only that the charges for sin against him are removed, and he is legally declared innocent on the basis of Christ's divine righteousness.
Justification is a judicial action by a judge—God. The term indicates an aligning of a forgiven person with a standard. In this case, the standard is the law of God. Justification does not happen automatically to all but solely to those whom God calls, forgives, and unites with Christ because they believe in the efficacy of His death as the divinely given Substitute to pay the death penalty for their sins. They have humbled themselves before Him and fervently desire to glorify God through a vastly changed life.
Character is a group of qualities that cannot be transferred by fiat. It is created throughout life, either by experiences in this world or by experiences within a relationship with God. We desire to be in the character image of God. In His purpose, the creating of godly character takes place during the sanctification process.
The New International Version renders Romans 10:17 as, "Consequently, faith comes from hearing the message, and the message is heard through the word of Christ." Paul uses "faith," one's belief, in the sense of trust. At the point of justification in a person's spiritual life, faith is not producing works; it is merely the mental activity of believing. The works come later as the sanctification process begins and continues. This faith, this trust, has its foundation in knowledge that God has supplied by enabling the called person to reach the right conclusion, a conclusion based in fact. His trust is therefore not blind; it is based, not on speculation, but truth.
In Galatians 2:18, Paul shows that being justified by faith does not lead to a life of sin. Being justified by faith indicates a commitment in the mind of the justified to go forward, building on the relationship by being established with Christ. Verse 19 begins with the word "for," indicating the reason why the justified person will not return to the old way of life. By faith, Paul understands the reason: As far as the law is concerned, he is dead. His debt to it has been satisfied.
Verse 20 continues the thought. Like Christ died, the "old man," the carnal Paul, also died and was symbolically buried in the waters of baptism. Also like Christ, he has been raised from the dead—symbolically—from the waters of baptism. This is done for the sole reason that, by means of the very faith of Christ that he has been given, he would live life as Christ lived. The life Christ lived was sinless. He did not break God's laws, and that is the objective of the new creation and salvation.
John W. Ritenbaugh
Living By Faith and God's Grace (Part Two)