Romans 9:25-33 // Righteousness By Faith

As he saith also in Osee, I will call them my people, which were not my people; and her beloved, which was not beloved. 26 And it shall come to pass, that in the place where it was said unto them, Ye are not my people; there shall they be called the children of the living God.
27 Esaias also crieth concerning Israel, Though the number of the children of Israel be as the sand of the sea, a remnant shall be saved: 28 For he will finish the work, and cut it short in righteousness: because a short work will the Lord make upon the earth.
29 And as Esaias said before, Except the Lord of Sabaoth had left us a seed, we had been as Sodoma, and been made like unto Gomorrha.
30 What shall we say then? That the Gentiles, which followed not after righteousness, have attained to righteousness, even the righteousness which is of faith. 31 But Israel, which followed after the law of righteousness, hath not attained to the law of righteousness. 32 Wherefore? Because they sought it not by faith, but as it were by the works of the law. For they stumbled at that stumblingstone; 33 As it is written, Behold, I lay in Sion a stumblingstone and rock of offence: and whosoever believeth on him shall not be ashamed. (Romans 9:25-33)

Jesus trips Jews up. Jews are offended by Jesus and Christianity, but if they believe on him, and some of them do, they would no longer be ashamed because the Hebrew Scriptures are not discarded but fulfilled in Jesus and Christianity. The Jews tried to obey the law by will power and multiplying rules, they were supposed to obey the law by faith. That is, to submit to the Spirit's leading and ask for the Father's mercy and meditate on the works of Jehovah as played out in the Hebrew Scriptures and not focus on their own sins or virtues but wait patiently for God to do a work in their hearts leading to righteousness. This is what the Gentiles, the Christians that is, have been doing; and they have obtained the righteousness that the Jews failed to obtain. Christians have mostly fallen away from this into antinomianism (doing away with the law) however.

Sometimes it is hard to know in detail what God's law teaches, but to major in majors: to focus on the points his word teaches us to focus on, this is a good place to start.