2 Peter 2:21-22

21It would have been better for them if they had never known God's good way. But they did understand about the right things that God wants us to do. And then they turned away from that way of life. They stopped obeying God's good rules, that people had taught them.

22You know these true proverbs: ‘After a dog has been sick, it returns to eat it again.’ Also: ‘After you wash a pig, it will quickly roll in the dirt again.’ These words describe how the false teachers live.