The entire verse is as follows:
“Death and life are in the hands of the tongue, and those that love it will eat its fruit.” (Mishlei: 18; 21)
Mitzudas David explains that Lashon HaRa leads to death at the hands of the tongue, while, words of Torah spoken with the tongue brings about life. “Those who love it”, meaning speaking a great deal, “will eat its fruit”, whether the reward for speaking Torah, or the punishment for speaking Lashon HaRa.
 Perhaps this is coming to teach us that since there is one mouth, in contrast to the eyes, nostrils, and ears, that one should limit their speech to a greater degree than that which they take in with their other senses. In fact, out of the five senses, the only sense that has one orifice is the sense of taste. One can feel with every part of their body, and possesses two eyes, two nostrils, and two ears.