Augustine of Hippo

But others think that the words, "Ye know what withholdeth," and "The mystery of iniquity worketh," refer only to the wicked and the hypocrites who are in the Church, until they reach a number so great as to furnish Antichrist with a great people, and that this is the mystery of iniquity, because it seems hidden; also that the apostle is exhorting the faithful tenaciously to hold the faith they hold when he says, "Only he who now holdeth, let him hold until he be taken out of the way," that is, until the mystery of iniquity which now is hidden departs from the Church. For they suppose that it is to this same mystery John alludes when in his epistle he says, "Little children, it is the last time: and as ye have heard that Antichrist shall come, even now are there many antichrists; whereby we know that it is the last time. They went out from us, but they were not of us; for if they had been of us, they would no doubt have continued with us." As therefore there went out from the Church many heretics, whom John calls "many antichrists," at that time prior to the end, and which John calls "the last time," so in the end they shall go out who do not belong to Christ, but to that last Antichrist, and then he shall be revealed.