John Chrysostom

"As concerning the Gospel, they are enemies for your sakes: but as touching the election, they are beloved for the fathers' sakes." That the Gentile then might not be puffed up, and say, "I am standing, do not tell me of what would have been, but what has been," he uses this consideration to bring him down, and says, "As concerning the Gospel, they are enemies for your sakes." For when you were called they became more captious. …

Homily on Romans 19 ↗

Theophylact of Ohrid

Since, he says, you have submitted to the Gospel and have been accepted by God, they became more stubborn and recoiled further and became enemies; but since their ancestors were chosen by God from the beginning, God will not allow them to perish completely (for they are beloved), but will accept them if they believe.

Commentary on Romans ↗

Thomas Aquinas

Then when he says, as concerning the Gospel, he proves his statement with a reason: first, he presents the proof; second, he removes an objection, at for the gifts and the calling. First, therefore, he says that their sins will be taken away and that after they have sins, they are enemies of Christ. As concerning the Gospel, indeed, which they resist, they are enemies for your sake, i.e., it has turned out to your benefit. …

Commentary on Romans ↗