The Pulpit Commentary - 2 Peter 2:19
While they promise them liberty; literally, promising. The words cohere closely with the preceding clause. Liberty was the subject of their great swelling words of vanity; they talked loudly, made a great boast, about liberty. Perhaps they were wresting to their own destruction the teaching of St. Paul concerning Christian liberty. St. Paul had spoken of the liberty of the glory of the children of God ( Romans 8:21 ); he had again and again asserted the liberty of Christians in things... read more
John Calvin's Commentary on the Bible - 2 Peter 2:21
Verse 21 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.... read more