Acts 20:29

These several matters, I pray you, suggest to our brethren. And as "he who humbleth himself shall be exalted," now is the time when they should rather fear the ensnaring adversary, who more eagerly attacks the man that is strongest, and becoming more virulent, for the very reason that he is conquered, strives to overcome his conqueror. The Lord grant that I may soon both see them again, and by salutary exhortation may establish their minds to preserve their glory. For I am grieved when I hear that some of them run about wickedly and proudly, and give themselves up to follies or to discords; that members of Christ, and even members that have confessed Christ, are defiled by unlawful concubinage, and cannot be ruled either by deacons or by presbyters, but cause that, by the wicked and evil characters of a few, the honourable glories of many and good confessors are tarnished; whom they ought to fear, lest, being condemned by their testimony and judgment, they be excluded from their fellowship. That, finally, is the illustrious and true confessor, concerning whom afterwards the Church does not blush, but boasts.

"For I know this, that after my departing shall grievous wolves enter in among you, not sparing the flock." Again he engages them from another quarter, from the things which should come after: as when he says, "We wrestle not against flesh and blood. After my departing," he says, "grievous wolves shall enter in among you" (Eph. vi. 12); twofold the evil, both that he himself would not be present, and that others would assail them. "Then why depart, if thou knowest this beforehand?" The Spirit draws me, he says. Both "wolves," and "grievous, not sparing the flock;" and what is worse, even "from among your own selves:" the grievous thing (this), when the war is moreover an intestine war. The matter is exceeding serious, for it is "the Church of the Lord:" great the peril for with blood He redeemed it: mighty the war, and twofold. "Also of your own selves shall men arise, speaking perverse things, to draw away disciples after them."

A twofold misfortune: on the one hand, that he will not be there, and on the other, that certain people will attack, and moreover — what is especially bitter — "from among your own selves." It is grievous when civil war breaks out.

For I know this,....

For I know this - By what he had seen in other places; by his knowledge of human nature, and of the dangers to which they were exposed; and by the guidance of inspiration. After my departure - His presence had been the means of guarding the church, and preserving it from these dangers. Now that the founder and guide of the church was to be removed, they would be exposed to dissensions and dangers. Grievous wolves - Heavy βαρεῖς bareis, strong, mighty, dangerous wolves - so strong that the feeble flock would not be able to resist them.