Thomas Aquinas, on Rom 9:28

“For he shall finish his word, and cut it short in justice; because a short word shall the Lord make upon the earth.”

“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 occasions for transgressing them and even added counsels of perfection. Thus he said to the young man who had kept all the precepts of the law: one thing is lacking to you. If you would be perfect, go and sell what you possess and give to the poor (Matt 19:21). For this reason he said to his disciples: you must be perfect, as your heavenly Father is perfect (Matt 5:48). The second efficacy is that the word is cut short. This is suitably joined to the first efficacy, because the more perfect a word is the more profound it is and, as a consequence, simpler and briefer. Now the word of the Gospel shortens the words of the law, because it included all the figurative sacrifices of the law in one true sacrifice, in which Christ offered himself as a victim for us (Eph 5:2). Furthermore, it includes all the moral precepts of the law in the two precepts of charity: on these two precepts depend the law and the prophets (Matt 22:40). Hence he says cut short in equity, either because nothing is omitted of the multitude of figures and precepts of the law, but all are included in the brevity of the Gospel; or because nothing remains of them to be observed but what is equitable according to the dictates of natural reason: all your commands are equitable (Ps 118:72). This should be understood so that the sense is: the word of the Gospel will shorten and perfect in equity. Second, when he says because a short word, he gives the reason for this efficacy, saying, for the Lord upon the earth, i.e., when he lives on earth as man: afterwards he was seen upon earth and conversed with men (Bar 3:38), will make a short word. For the word which the Lord himself spoke in the flesh should be more perfect and powerful than the words he spoke through the prophets, as it says in Hebrews: God, who, at sundry time and in diverse manners, spoke of old to our fathers by the prophets, in these last days he has spoken to us through his Son (Heb 1:1). Or, in another way: for the Lord, i.e., God the Father, will make a short word, i.e., incarnate, because the Son of God emptied himself, taking the form of a slave. He is called brief, not because anything was subtracted from the fullness or greatness of his divinity, but because he underwent our exile and smallness. This decree is considered, however, in Isaiah, where according to our account it is thus said: for if your people, O Israel, shall be as the sand of the sea, a remnant of them shall be converted. The abridged consumption shall overflow with justice. For the Lord God of hosts shall make a consumption, and an abridgment in the midst of all the land (Isa 10:22–23).”

Imported from an open dataset — not yet checked against the printed edition.