Paul did not let the Jewish man (person) think that their national standing made them right in the eyes of God, but neither did he want them to think there was no positive blessing to that relationship. While some were making false accusations, Paul wanted them to understand two things: first, consistency demonstrates the accusation to be false; second, the law under which they lived made clear that they, too, were guilty before God (3:1-20). In order to be right (justified) in the eyes of God, one must come to Him in faith. Faith is that human response that calls upon God to save (cf. Acts 2:21). This is not something new (and exclusive) to the New Testament, but it is also a doctrine of the Old Testament (cf. Deuteronomy 10:12-16; Habakkuk 2:4). Those who come to God by faith actually fulfill a purpose of the old covenant (cf. John 6:44-45; Galatians 3:23-27).
Earlier in the chapter Paul anticipated an objection that would be given him concerning the value of being a Jew; the Jews, Paul said, had entrusted to them the word of God. There is great value to that. In Exodus 19 the Lord called upon Israel to be a kingdom of priests (19:6). In the New Testament there is a similar exhortation to godliness (1 Peter 2:5, 9). It would be a shame of great proportion if even one New Testament Christian adopted the attitude that many Jews adopted: “Since I am a member of the Israelite community (or, the Lord’s church), my standing before the Lord is secure.” There is great security in being a member of the Lord’s body; that security is weakened, however, when we begin to lose sight of who Jesus is and that we depend on Him. If you live in a house and do nothing to tend to the needs of the house the house will eventually crumble.