John Chrysostom

"What then? Israel hath not obtained that, which he seeketh for; but the election hath obtained it and the rest were blinded." He had said that God did not cast off His people; and to show in what sense He had not cast them off, he takes refuge in the Prophets again. And having shown by them that the more part of the Jews were lost, that he might not seem to be again bringing forward an accusation of his own, and to make his discourse offensive, and to be attacking them as enemies, he takes refuge in David and Isaiah. …

Homily on Romans 19 ↗

Theophylact of Ohrid

Having explained what grace is, that is, that it is a gift of God apart from works, he says that the Israelites, seeking righteousness, did not obtain it, because they sought it poorly and from works, by which it is impossible to obtain it. "But the elect obtained it." By the word "obtained" he shows the greatness of the blessings and that everything is the work of God's grace. And in ordinary conversation we too say: he obtained a profit, that is, he acquired a gain without labor.

Commentary on Romans ↗

Thomas Aquinas

Then when he says, what then, he draws the conclusion he intended. And first he sets it out, saying what then shall we say follows from what has been said? This, namely, that Israel, as far as the greater part of its people was concerned, has not obtained that which it sought, namely, justice. This is the way one must interpret what was said above: but Israel, by following after the law of justice, is not come unto the law of justice (Rom 9:31). You shall seek me, and shall not find me (John 7:34). …

Commentary on Romans ↗