2 Peter 2:18-19

‘For, uttering great swelling words of vanity, they entice in the lusts of the flesh, by lasciviousness, those who are just escaping from those who live in error, promising them liberty, while they themselves are bondservants of corruption.'

Peter then expands on what he means. Their teaching is made up of great swellings of vanity, their attraction and lure is through the lusts of the flesh, which appeal to men's worst natures. Everything is from the wrong motive and directed towards the wrong ends. And what is worse they do it to those who have newly become connected with the Christian church, who were only just escaping from a former life which offered these things, a life where they had lived among those who lived in error. Thus they are being dragged back by these teachers into the kind of life that they have just recently escaped from.

‘Promising them liberty.' These false teachers pretend to offer them freedom, while the truth is that they themselves are enslaved, bondslaves of corruption. So rather than becoming truly free, they will become slaves to things that will destroy them.

The promise of freedom was a characteristic of Christian teaching. The Gospel offers men a genuine freedom from sin and the world. But Paul warns his readers that while they have indeed been called to freedom they must not use it for an occasion to the flesh (Galatians 5:13). Compare how in his first letter Peter tells his people that indeed they are free but they must not use their freedom as a cloak of maliciousness (1 Peter 2:16). For the point is that Christian freedom is not the freedom to sin, but is freedom from sin. But these false teachers offered to men the freedom to sin as much as they liked, with the result that they simply bring them into bondage to sin.