Romans 9:30-33
Israel's Unbelief
30What then shall we say? That the Gentiles, who did not pursue righteousness, have obtained it, a righteousness that is by faith; 31but Israel, who pursued a law of righteousness, has not attained it. 32Why not? Because they pursued it not by faith but as if it were by works. They stumbled over the "stumbling stone." 33As it is written:
"See, I lay in Zion a stone that causes men to stumble
and a rock that makes them fall,
and the one who trusts in him will never be put to shame."
St. Paul tells us that the Gentiles are new coverts to Jesus and are seeking Him through faith...But Israeli, who are God's people, and have the law of righteousness (the Law of Moses) still seek their righteousness through their works on earth...But St. Paul teaches that we are awarded heaven by God's grace and not our works, so the Israeli's are stumbling over the stumbling stone...
The Israeli people did not pursue Jesus and His teachings...They did not put their faith in Him...They embraced the Mosaic Law and tried to follow rules to get to the kingdom of God...St. Paul quotes Isaiah 8:14, 28:16 to teach us that Jesus could be a stumbling stone and rock that makes us fall, if we do not trust Him...