John Chrysostom

"And except those days should be shortened, there should no flesh be saved; but for the elect's sake those days shall be shortened." By these things He shows them to be deserving of a more grievous punishment than had been mentioned, speaking now of the days of the war and of that siege. But what He saith is like this. If, saith He, the war of the Romans against the city had prevailed further, all the Jews had perished (for by "no flesh" here, He meaneth no Jewish flesh), both those abroad, and those at home. …

Homily on the Gospel of Matthew 76 ↗

Augustine of Hippo

For we ought not to doubt that when Jerusalem was overthrown, there were among that people elect of God who had believed out of the circumcision, or would have believed, elect before the foundation of the world, for whose sake those days should be shortened, and their evils made endurable. Some there are who suppose that the days will be shortened by a more rapid motion of the sun, as the day was made longer on the prayer of Jesus Naue.

Catena Aurea by Aquinas ↗

Jerome

And unless those days had been shortened, no flesh would be saved; but for the sake of the elect those days will be shortened. The shortened days, not according to the delusions of some (who think that the moments of time can be changed; and do not remember that writing: Your ordinance endures (Ps. CXVIII, 91)), but we should understand it according to the quality of time, that is, the days are shortened not in measure, but in number; just as in the blessing it is said; I will satisfy him with long life (Ps. …

Commentary on Matthew ↗

Thomas Aquinas

Hence, unless those days had been shortened, no flesh should be saved. Augustine says that some have explained this as meaning that the days were then made shorter, as in the time of Joshua a day was made longer. But against this Psalm 118:91 says: By thy ordinance the days continue; therefore it can be said in two ways. First, that the days of tribulation were shortened in number. Hence, if that time had lasted longer, all would have been killed, because none would have remained. And why? …

Commentary on Matthew ↗