17 But if you call yourself a Jew and rely on the law and boast in God
18 and know his will and approve what is excellent, because you are instructed from the law;
19 and if you are sure that you yourself are a guide to the blind, a light to those who are in darkness,
20 an instructor of the foolish, a teacher of children, having in the law the embodiment of knowledge and truth-
21 you then who teach others, do you not teach yourself? While you preach against stealing, do you steal?
22 You who say that one must not commit adultery, do you commit adultery? You who abhor idols, do you rob temples?
23 You who boast in the law dishonor God by breaking the law. – Romans 2:17-23
Paul is trying to get the message across to the believers who are trusting that their Jewish law and traditions will bring them into the Kingdom of God. The Jewish belief was that they were a chosen people who had a covenant with God through which they were saved. So by being born into a Jewish family or by being accepted into the Jewish faith they were destined to go to heaven. The Jewish people were to be a light to the world and were to teach the nations about God. They were to bring light to the blind and teach the foolish:
And I will lead the blind in a way that they do not know, in paths that they have not known I will guide them. I will turn the darkness before them into light, the rough places into level ground. These are the things I do, and I do not forsake them. – Isaiah 42:16
Paul points out however that there is hypocrisy in their teaching, asking if the very behavior they preach against they are performing? Keeping the law never brings glory to God. Walking humbly before Him does. Obedience to God leads to salvation not keeping rituals. Loving your neighbor not loving the law. Possessing the law did not lead to salvation, knowing the Author of the law does. The law sometimes refers to the Old Testament, especially the Pentateuch, the five Books of Moses. God had revealed Himself through the scriptures over the generations. There is great wisdom and you can get to understand the mind and heart of God. But it is not the knowledge that saves you but the person of Jesus Christ. His death on the cross was the most significant historical event in all time. All history prior to His death and resurrection led up to it and all subsequent history and the future is effected by it. The law pointed to it as it was God’s plan of redemption that the law would be fulfilled in Jesus:
44 Then he said to them, “These are my words that I spoke to you while I was still with you, that everything written about me in the Law of Moses and the Prophets and the Psalms must be fulfilled.”
45 Then he opened their minds to understand the Scriptures,
46 and said to them, “Thus it is written, that the Christ should suffer and on the third day rise from the dead,
47 and that repentance for the forgiveness of sins should be proclaimed in his name to all nations, beginning from Jerusalem. – Luke 24:44-47
For the whole law is fulfilled in one word: “You shall love your neighbor as yourself.” – Galatians 5:14