“So, what are we to say? This: that Gentiles, even though they were not striving for righteousness, have obtained righteousness; but it is a righteousness grounded in trusting!
However, Isra’el, even though they kept pursuing a Torah that offers righteousness, did not reach what the Torah offers. Why?
Because they did not pursue righteousness as being grounded in trusting but as if it were grounded in doing legalistic works. They stumbled over the stone that makes people stumble.
(I’d say in addition to this that many Christians of today also stumble over the rock that trips them up in not pursuing the Torah of righteousness. They trust in the Messiah without doing the works of righteousness, while some Jews do the works of righteousness without trusting in the Messiah.)
As the Tanakh puts it, “Look, I am laying in Tziyon a stone that will make people stumble, a rock that will trip them up. But he who rests his trust on it will not be humiliated.””
Romans (Rom) 9:30-33 CJB