2 Peter 2:19

Verse 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.