John Chrysostom

"He will finish the work, and cut it short in righteousness," he says, "because a short work will the Lord make upon the earth." What he means then is somewhat of this sort. There is no need of fetching a circuit, and of trouble, and the vexation of the works of the Law, for the salvation is by a very short way. For such is faith, it holds salvation in a few short words. …

Homily on Romans 16 ↗

Theophylact of Ohrid

Now he shows how the remnant will be saved, and says that there is no need to labor, to go far, and to exhaust oneself with works of the law. God, he says, who brings to completion and accomplishes the word of faith in a short way throughout all the earth, will do this "in righteousness," that is, in order to justify those who have accepted it. "If you confess with your mouth Jesus as Lord, and believe in your heart that God raised Him from the dead, you will be saved" (Rom. 10:9). …

Commentary on Romans ↗

Thomas Aquinas

Second, at for he shall finish his word, he cites the cause of salvation: first, the efficacy of the word of the Gospel, saying: for he shall finish his word and cut it short in equity. Note here a twofold efficacy of the evangelical word. The first is that the word is fulfilling, i.e., perfective: the law made nothing perfect (Heb 7:19); but the Lord says, I have come not to abolish the law but to fulfill (Matt 5:17), because he applied the truth to the figures of the law, explained the moral precepts of the law properly, removed …

Commentary on Romans ↗