John Chrysostom
By the tribulation, He means the times of Antichrist and the false Prophets; for when there are so many deceivers, the tribulation will be great. But it shall not extend through any great length of time. For if for the elect’s sake the Jewish war is shortened, much more shall this tribulation be shortened for their sakes; for which reason He said not After, but Immediately after, for He shall come immediately after.
Very fitly shall they be shaken and dismayed, seeing so mighty a change being wrought, their fellow-servants punished, and the universe standing before a terrible tribunal.
But because the sun will be darkened, the cross would not be seen, if it were not far brighter than the rays of the sun. That the disciples might not be ashamed, and grieve over the cross, He speaks of it as a sign, with a kind of distinction. The sign of the cross will appear to overthrow the shamelessness of the Jews, when Christ shall appear in the judgment, shewing not only His wounds, but His most ignominious death, And then all the tribes of the earth shall mourn. For when they shall see the cross, they shall bethink them how they have gained nought by His death, and that they have crucified Him whom they ought to have worshipped.
He adds this, that having heard of the cross, they should not now imagine a similar degradation.