Proverbs 18:21

Note, 1. A man may do a great deal of good, or a great deal of hurt, both to others and to himself, according to the use he makes of his tongue. Many a one has been his own death by a foul tongue, or the death of others by a false tongue; and, on the contrary, many a one has saved his own life, or procured the comfort of it, by a prudent gentle tongue, and saved the lives of others by a seasonable testimony or intercession for them. And, if by our words we must be justified or condemned, death and life are, no doubt, in the power of the tongue. Tongues were Aesop's best meat, and his worst. 2. Men's words will be judged of by the affections with which they speak; he that not only speaks aright (which a bad man may do to save his credit or please his company), but loves to speak so, speaks well of choice, and with delight, to him it will be life; and he that not only speaks amiss (which a good man may do through inadvertency), but loves to speak so (Psa 52:4), to him it will be death. As men love it they shall eat the fruit of it.

— Matthew Henry's Concise Commentary (public domain)

Death and life--or, the greatest evil and good. that love it--that is, the tongue, or its use for good or evil. eat . . . fruit--(Compare Pro 18:19; Jam 1:19).

— Jamieson-Fausset-Brown Commentary (public domain)