2-peter 2:19

While they promise them liberty - Either to live in the highest degrees of spiritual good, or a freedom from the Roman yoke; or from the yoke of the law, or what they might term needless restraints. Their own conduct showed the falsity of their system; for they were slaves to every disgraceful lust.

For of whom a man is overcome - This is an allusion to the ancient custom of selling for slaves those whom they had conquered and captivated in war. The ancient law was, that a man might either kill him whom he overcame in battle, or keep him for a slave. These were called servi, slaves, from the verb servare, to keep or preserve. And they were also called mancipia, from manu capiuntur, they are taken captive by the hand of their enemy. Thus the person who is overcome by his lusts is represented as being the slave of those lusts. See Romans 6:16, and the note there.

While they promise them liberty - True religion always promises and produces liberty (see the notes at John 8:36), but the particular liberty which these persons seem to have promised, was freedom from what they regarded as needless restraint, or from strict and narrow views of religion.

They themselves are the servants of corruption - They are the slaves of gross and corrupt passions, themselves utter strangers to freedom, and bound in the chains of servitude. These passions and appetites have obtained the entire mastery over them, and brought them into the severest bondage. This is often the case with those who deride the restraints of serious piety. They are themselves the slaves of appetite, or of the rules of fashionable life, or of the laws of honor, or of vicious indulgences. "He is a freeman whom the truth makes free, and all are slaves besides." Compare the notes at 2 Corinthians 3:17.

For of whom a man is overcome ... - Or rather "by what (ᾧ hō) anyone is overcome;" that is, "whatever" gets the mastery of him, whether it be avarice, or sensuality, or pride, or any form of error. See the notes at Romans 6:16, where this sentiment is explained.

2:19 While they promise them liberty - From needless restraints and scruples; from the bondage of the law.Themselves are slaves of corruption - Even sin, the vilest of all bondage.