C. F. Keil and Franz Delitzsch on Proverbs 16:27

Pro 16:27 27 A worthless man diggeth evil;      And on his lips is, as it were, scorching fire.

Regarding אישׁ בּליּעל, vid., Pro 6:12, and regarding כּרה, to dig round, or to bore out, vid., at Gen 49:5; Gen 50:5; here the figure, “to dig for others a pit,” Pro 26:27, Psa 7:16, etc.: to dig evil is equivalent to, to seek to prepare such for others. צרבת Kimchi rightly explains as a form similar to קשּׁבת; as a subst. it means, Lev 13:23, the mark of fire (the healed mark of a carbuncle), here as an adj. of a fire, although not flaming (אשׁ להבה, Isa 4:5, etc.); yet so much the hotter, and scorching everything that comes near to it (from צרב, to be scorched, cogn. שׁרב, to which also שׂרף is perhaps related as a stronger power, like comburere to adurere). The meaning is clear: a worthless man, i.e., a man whose disposition and conduct are the direct contrast of usefulness and piety, uses words which, like an iron glowing hot, scorches and burns; his tongue is φλογιζομένη ὑπὸ τῆς γεέννης (Jam 3:6).