R. Yonah #1: Healing of the tongue is very esteemed. Other cures and salves, sometimes they work, and sometimes they do not save. However, healing of the tongue cannot be without benefit, just like Etz ha'Chayim; the cure of its fruits always helps. When a Chacham rebukes someone proper to receive rebuke, it cannot be that the words of rebuke will not enter the heart of the receiver if the rebuke is constant. He will totally or partially fix his ways. Therefore, the one who rebukes will not despair and the receiver will not weary. This is for those who want to hear rebuke, just like Etz ha'Chayim helps those who take from its fruits and eat. It does not help Evilim and Letzim, who hate rebuke - "Al Yochach Letz Pen Yisna'echa", "Yoser Letz Loke'ach Lo Kalon u'Mochi'ach l'Rasha Mumo" (9:8, 7). Therefore, after our verse it says "Evvil Yin'atz Musar Aviv" to teach that Refu'as ha'Lashon will not help him. The previous verse said "Leshon Chachamim Teitiv Da'as" - they beautify words of Da'as, to the point that their Musar is accepted.

R. Yonah #2: Refu'ah of the tongue is very esteemed, for other cures remove the illness, but do not add to what he should live. Refu'ah of the tongue adds life, for via rebuke one finds the way of life - 'v'Derech Chayim Tochachas Musar" (6:23).

R. Yonah #3: Marpei Lashon is appeasement and consolation to reconcile friends - one who appeases [comforts an Oni] with words is greater than all of them (one who gives Tzedakah). It says "Koshel Yekimun Milecha" (Iyov 4:4).

Sha'arei Teshuvah (4:16): Torah is a cure for every wound.

Malbim: Eitz Chayim is a Refu'ah for illness of the tongue. He engages in Torah and Chachmah - "Etz Chayim Hi la'Machazikim Bah (3:18). This heals the tongue, like medicinal wood heals every illness. One who does not use this cure, and via enticement of the tongue, he does not eat from Eitz ha'Chayim, only from Eitz ha'Da'as Tov va'Ra, which brought death to the world via the first Ba'al Leshon ha'Ra (the snake ¹ ); he deviates with his tongue. This shows that his inner Ru'ach is broken, and he has an evil Ru'ach.

Rashi: One who is crooked with his mouth, in the end Hashem will bring breakage on him with the east wind, which is prepared to punish Resha'im - "b'Ru'ach Kadim Azah" (Shemos 14:21), "b'Ru'ach Kadim Afitzem" (Yirmeyah 18:18) "b'Ru'ach Kadim Teshaber Aniyos Tarshish" (Tehilim 48:8).

R. Yonah: Just like the tongue is the most esteemed cure, so the illness from the tongue - crooked speech, is worse than bodily illness. It breaks the Ru'ach; "Ru'ach Ish Yechalkel Machalehu v'Ru'ach Neche'ah Mi Yisa'enu" (18:14). Illness from the tongue is the disgrace, mockery and grief from blushing. One who makes another blush in public has no share in the world to come (Avos 3:11).

Malbim: Selef of the tongue is a tongue that veers from the way of Chachmah, and speaks Leshon ha'Ra and Rechilus [and all the more so when it makes crooked Binah; Stam Lashon refers to speech of Tevunah]. This breaks the Ru'ach. Speech is man's essence; one who makes it crooked, this is from an inner breakage whose root is in man's Ru'ach. The Ru'ach is broken; he is ill, and not complete. One who ruins the animalistic powers of the Nefesh, this is a breakage in the animalistic Nefesh. It is not as dangerous as a broken Ru'ach.