17 Who then is the blessed man, that shall at that time devoutly witness for Christ? For I say that the Martyrs of that time excel all martyrs. For the Martyrs hitherto have wrestled with men only; but in the time of Antichrist they shall do battle with Satan in his own person. And former persecuting kings only put to death; they did not pretend to raise the dead, nor did they make false shows of signs and wonders. But in his time there shall be the evil inducement both of fear and of deceit, so that if it be possible the very elect shall be deceived. Let it never enter into the heart of any then alive to ask, “What did Christ more?
For by what power does this man work these things? Were it not God's will, He would not have allowed them.” The Apostle warns you, and says beforehand, And for this cause God shall send them a working of error; (send, that is, shall allow to happen;) not that they might make excuse, but that they might be condemned. Wherefore? They, he says, who believed not the truth, that is, the true Christ, but had pleasure in unrighteousness, that is, in Antichrist.
But as in the persecutions which happen from time to time, so also then God will permit these things, not because He wants power to hinder them, but because according to His wont He will through patience crown His own champions like as He did His Prophets and Apostles; to the end that having toiled for a little while they may inherit the eternal kingdom of heaven, according to that which Daniel says, And at that time your people shall be delivered, every one that shall be found written in the book (manifestly, the book of life); and many of them that sleep in the dust of the earth shall awake, some to everlasting life, and same to shame and everlasting contempt; and they that be wise shall shine as the brightness of the firmament; and of the many righteous, as the stars for ever and ever.
Source: Catechetical Lectures (New Advent)