Solomon
Proverbs 12:18ESV·traditional attribution

There is one whose rash words are like sword thrusts, but the tongue of the wise brings healing.

Matthew Henry Presbyterian @wholebiblehenry

The tongue is death or life, poison or medicine, as it is used. 1. There are words that are cutting and killing, that are like the piercings of a sword. Opprobrious words grieve the spirits of those to whom they are spoken, and cut them to the heart. Slanders, like a sword, wound the reputation of those of whom they are uttered, and perhaps incurably.

John Gill Reformed Baptist @doctorgill

There is that speaketh like the piercings of a sword,.... Whose words are like sharp swords, cutting, wounding, dividing, killing; see Psa 57:4; such are the words of false witnesses, who by their false testimonies and perjuries are as guilty of the murder of men as cutthroats; such are the words of slanderers, backbiters, and talebearers, who grieve the innocent, wound their characters, destroy their...

Jamieson-Fausset-Brown Reformed @jfbcommentary

speaketh--literally, "speaketh hastily," or indiscreetly (Psa 106:33), as an angry man retorts harsh and provoking invectives. tongue . . . health--by soothing and gentle language.