20. For if after. He again shews how pernicious was the sect which led men consecrated to God back again to their old filth and the corruptions of the world. And he exhibits the heinousness of the evil by a comparison; for it was no common sin to depart from the holy doctrine of God. It would have been better for them, he says, not to have known the way of righteousness; for though there is no excuse for ignorance, yet the servant who knowingly and wilfully despises the commands of his lord, deserves a twofold punishment. There was besides ingratitude, because they wilfully extinguished the light of God, rejected the favor conferred on them, and having shaken off the yoke, became perversely wanton against God; yea, as far as they could, they profaned and abrogated the inviolable covenant of God, which had been ratified by the blood of Christ. The more earnest then ought we to be, to advance humbly and carefully in the course of our calling. We must now consider each sentence.

By naming the pollutions of the world, he shews that we roll in filth and are wholly polluted, until we renounce the world. By the knowledge of Christ he no doubt understands the gospel. He testifies that the design of it is, to deliver us from the defilements of the world, and to lead us far away from them. For the same reason he afterwards calls it the way of righteousness. He then alone makes a right progress in the gospel who faithfully learns Christ; and he truly knows Christ, who has been taught by him to put off the old man and to put on the new man, as Paul reminds us in Ephesians 4:22. ¹

21. By saying that having forsaken the commandment delivered unto them, they returned to their own pollutions, he intimates first, how inexcusable they were; and secondly, he reminds us that the doctrine of a holy and virtuous life, though common to all and indiscriminately belonging to all, is yet peculiarly taught to those whom God favors with the light of his gospel. But he declares that they who make themselves slaves again to the pollutions of the world fall away from the gospel. The faithful also do indeed sin; but as they allow not dominion to sin, they do not fall away from the grace of God, nor do they renounce the profession of sound doctrine which they have once embraced. For they are not to be deemed conquered, while they strenuously resist the flesh and its lusts.

22. But it has happened unto them. As the example disturbs many, when men who had submitted to the obedience of Christ, rush headlong into vices without fear or shame, the Apostle, in order to remove the offense, says that this happens through their own fault, and that because they are pigs and dogs. It hence follows that no part of the sin can be ascribed to the gospel.

For this purpose he quotes two ancient proverbs, the first of which is found as the saying of Solomon in Proverbs 26:11. But what Peter meant is briefly this, that the gospel is a medicine which purges us by wholesome vomiting, but that there are many dogs who swallow again what they have vomited to their own ruin; and that the gospel is also a laver which cleanses all our uncleanness, but that there are many swine who, immediately after washing, roll themselves again in the mud. At the same time the godly are reminded to take heed to themselves, except they wish to be deemed dogs or swine.