This verse speaks about two kinds of people who will change for the better under the new regime: those who are impulsive and those who mumble.

The mind of the rash will have good judgment: Rash people are those who act hastily, usually without carefully considering the outcome of their actions. Good News Translation says they are “impatient.” Revised English Bible expresses the meaning well with “impetuous.” Such a person’s mind … will have good judgment (literally “heart will understand to know”). Rather than always being impulsive, they will now be discerning. They will reflect carefully before acting, in contrast with their former lack of careful thought. For this line New Jerusalem Bible translates “the heart of the hasty will learn to think things over.”

And the tongue of the stammerers will speak readily and distinctly is literally “and the tongue of the mumblers will be quick to speak clearly.” Those whose speech was hard to understand will now speak fluently and clearly. Stammerers renders a Hebrew adjective, which comes from a root meaning “to speak inarticulately/unclearly.” A better rendering may be “those who mumble” (similarly New Jewish Publication Society’s Tanakh). The adverb readily renders the same Hebrew verb as the participle translated rash. Here it conveys that these people will be able to speak fluently. The second adverb distinctly translates a Hebrew adjective meaning “clear” or “glowing.” Here it means these people will be able to speak clearly.

Translation examples for this verse are:

• Those who are impetuous will think before they act,
those who are mumblers will speak fluently and clearly.

• The minds of the hasty will think matters through,
the tongues of those who mumble will speak smoothly and with clarity.

• The hasty will have understanding and knowledge,
the stutterers will speak quickly and clearly.

Quoted with permission from Ogden, Graham S. and Sterk, Jan. A Handbook on Isaiah. (UBS Helps for Translators). New York: UBS, 2011. For this and other handbooks for translators see here .