2 Peter 2:21-22

For never to have obtained a [full, personal] knowledge of the way of righteousness would have been better for them than, having obtained [such knowledge], to turn back from the holy commandment which was [verbally] delivered to them. There has befallen them the thing spoken of in the true proverb, The dog turns back to his own vomit, and, The sow is washed only to wallow again in the mire. [Prov. 26:11.]