Burning lips and a wicked heart are like a potsherd covered with silver dross.
This may be meant either, 1. Of a wicked heart showing itself in burning lips, furious, passionate, outrageous words, burning in malice, and persecuting those to whom, or of whom, they are spoken; ill words and ill-will agree as well together as a potsherd and the dross of silver, which, now that the pot is broken and the dross separated from the silver, are fit...
He that hateth dissembleth with his lips,.... He that bears a grudge in his mind, and retains hatred in his heart against any person, hides it all he can, till he has an opportunity of showing it as he would; he pretends a great deal of friendship with his lips, that his hatred might not be known; he would be thought to be a friend...
Warm professions can no more give value to insincerity than silver coating to rude earthenware.