What do we learn from "Maves v'Chayim b'Yad ha'Leshon"?
Erchin 15b 1 : One who wants to live should use his tongue (to speak Divrei Torah). One who wants to die should use his tongue (for Lashon ha'Ra).
Orchos Tzadikim (Sha'ar Leshon ha'Ra DH Kesiv citing Shocher Tov 39:2): It can cause a person to be killed or saved, like in the story of the man who brought lion's milk to the king and said 'it is dog's milk.'
Orchos Tzadikim (Sha'ar ha'Shetikah DH Mi): One who is used to minimizing words, he will not reveal [secrets]. Also, he is not used to tale-bearing. One [who speaks too much] does with his tongue more than with his sword. One can stand hear and [verbally] hand his colleague over to be killed, from afar. A sword kills only nearby. Therefore, man was created with two eyes, ears and nostrils, but only one mouth.
Orchos Tzadikim (Sha'ar Leshon ha'Ra DH Kesiv): Keneses Yisrael is beloved with its voice - "Hashmi'in it Es Kolech Ki Kolech Arev" (Shir ha'Shirim 2:14). It is hated with its voice - "Nasnah Alai b'Kolah Al Ken Seneisiha" (Yirmeyah 12:8).
Malbim: The tongue represents elevated speech of Tevunah. He speaks of comparisons of Tevunah, via which he understands a matter amidst another matter. With it, he judges between Emes and Sheker. Death and life depend on these! One who believes in the fundamentals of Emunah via comparisons of Tevunah, he will live. One who goes in a crooked path and denies Hashem's existence, Hashgachah and reward and punishment, he will die. This depends on the tongue, i.e. Binah.
Malbim (13:2): Lashon is Binah, which distinguish Emes from Sheker; good and bad do not depend on it, rather, life and death; it is Eitz ha'Chayim.
Initially, the Gemara learned from the verse that tongue can kill just like the hand. However, it concludes that another verse already taught this. (PF)
Why does it say "v'Ohaveha Yochal Piryah"?
Rashi: One who loves his tongue, and habituates it to Torah, he consumes the reward in this world.
R. Yonah: Since death and life are in the tongue's power, one who loves the tongue - he is one who loves to speak constantly, he should strive to get reward, and speak words of Chachmah, rebuke of life, Shalom and Emes. He will eat the fruits of the tongue; his reward will be great, for "Chayim b'Yad ha'Leshon." He should beware of Leshon ha'Ra, for "Maves
