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.