This short pericope concludes Paul's argument concerning Israel's past election and begins the train of thought that he continued in chapter 10. The use of "righteousness"ten times in 9:30-10:21 illustrates the unity of this section and identifies a major theme in it.
9:30-31 Paul's question, that often marks a new argument in Romans, introduced his concluding summary that he couched in terminology suggestive of a foot race. Israel struggled hard to obtain the prize of justification but crossed the finish line behind Gentiles who were not running that hard. Israel as a whole hoped to gain justification by doing good works, but believing Gentiles obtained the prize by believing the gospel.
"Hardly a passage in the New Testament is stronger than this one in its exposure of the futility of works as a means of justification."313
9:32-23 Israel as a whole, excluding the believing remnant, failed to gain a righteous standing before God because she tried to win it with works. A stone on the race track over which she stumbled impeded her progress. Intent on winning in her own effort Israel failed to recognize the Stone prophesied in Scripture who was to provide salvation for her.
The quotation is from Isaiah 8:14 and 28:16 (cf. 1 Pet. 2:6-8). God intended the Messiah to be the provider of salvation. However the Jews did not allow Him to fulfill this function for them. Consequently this Stone became a stumbling block for them (cf. 1 Cor. 1:23).
Israel's rejection of Jesus Christ did not make God unfaithful or unrighteous in His dealings with the nation. What it did do was make it possible for Gentiles to surpass the Jews as the main recipients of salvation.
(NT only) to listen to the NET Bible 
