Proverbs 15:28 New English Translation

²⁸The heart^[a] of the righteous considers^[b] how^[c] to answer,^[d]
but the mouth of the wicked pours out evil things.^[e]

Proverbs 15:28 tn Or “mind.” The term לֵב (lev) can refer to the “mind” or “heart” and represent a person’s thinking, feeling, or will.
Proverbs 15:28 tn The verb יֶהְגֶּה (yehgeh) means “to muse; to meditate; to consider; to study.” It also involves planning, such as with the wicked “planning” a vain thing (Ps 2:1, which is contrasted with the righteous who “meditate” in the law [1:2]).
Proverbs 15:28 tn The word “how” is supplied in the translation for stylistic reasons.
Proverbs 15:28 tc The LXX reads: “the hearts of the righteous meditate faithfulness.”sn The advice of the proverb is to say less but better things. The wise—here called the righteous—are cautious in how they respond to others. They think about it (heart = mind) before speaking.
Proverbs 15:28 sn The form is plural. What they say (the “mouth” is a metonymy of cause) is any range of harmful things.

New English Translation (NET)