People who cause conflict by what they say are spoken of as if they had tongues of serpents. Of course, snakes do not do damage with their tongues, but with their bites and especially with poison. Neither can a person make his tongue sharp. Instead, here the idea of a sharp tongue stands for speaking in a way to cause trouble. And the idea the snakes have sharp tongues stands for the fact that many of them have poison. (See: [[rc://en/ta/man/translate/figs-metaphor]])