2 Peter 2:19

While they promise them liberty
Not Christian liberty, which lies in a freedom from sin, its dominion, guilt, and condemnation, and in serving God with liberty, cheerfulness, and without fear; but a sinful carnal liberty, a liberty from the law of God, from obedience to it as a rule of walk and conversation, and from the laws of men, from subjection to the civil magistrate, and from servitude to masters, and obedience to parents; a liberty to lay aside and neglect the ordinances of the Gospel at pleasure, and to live in all manner of sin and wickedness; a liberty which is contrary to the nature, will, and work of Christ, to his Spirit, and to the principle of grace in the heart, and to the Gospel, and to the conduct and conversation of real saints. Now this was the snare by which the false teachers beguiled unstable souls; liberty being what is greatly desirable to men, and is suited to their carnal lusts and interests: but a vain promise was this, when

they themselves are the servants of corruption;
of sin, which has corrupted all mankind in soul and body; and particularly the lust of uncleanness, which these men walked in, and by which they not only corrupted themselves, but the good manners of others also; and which tended and led them both to ruin and destruction, signified by the pit of corruption: and yet these very preachers, that promised liberty to others, were the servants of sin; they were under the power and government of sin. They were not only born so, and were homeborn slaves to sin, but they sold themselves to work wickedness; voluntarily and with delight, they served divers lusts and pleasures, and were slaves and drudges thereunto; as likewise to Satan, whose lusts they would do, and by whom they were led captive; so that their condition was mean, base, and deplorable, and therefore could never make good their promise, or give that which they had not themselves: and which is confirmed by the following reasoning,

for of whom a man is overcome, of the same is he brought in bondage:
as this is a certain point in war, that when one man is conquered by another, he is no longer a free man, but the other's prisoner and captive, and is in a state of servitude and bondage; so it is when a man is overcome by sin, which must be understood not of a partial victory or conquest, for a good man may be surprised by sin, and overtaken in a fault, and be overcome and carried captive by it for a time, as was the apostle, see ( Romans 7:23 ) ( Galatians 6:1 ) ; and yet not be a servant of corruption, or properly in a state of bondage to it; but this is to be understood of a total and complete victory, when a man is wholly under the dominion of sin, it reigns in his mortal body, and he obeys it in the lusts of it, and yields his members instruments of unrighteousness; such a man is neither a free man himself, nor can he much less promise and give liberty to others.