Verses 29-30 (and also verse 33) share the common theme of control of emotions. Verse 29 expresses the idea that a quick temper is a sign of lack of good sense.

“He who is slow to anger has great understanding”: This line is concise and is literally “long of face, much understanding.” New Revised Standard Version has revised “He who” to “Whoever.” “Slow to anger”, that is, “does not get angry quickly,” is expressed figuratively in some languages; for example, “sits on his hot heart,” “makes quiet his liver,” “keeps his innermost silent,” or “doesn’t get hot inside quickly.” “Great understanding” means to “have good sense,” “be very wise,” “show great intelligence or insight.”

“But he who has a hasty temper exalts folly”: This line contrasts with the first. “A hasty temper” is literally “short spirit.” This is expressed in some languages as “hot heart,” “shaky liver,” or “he fires up quick” (see verse 17). “Exalts”, based on a verb meaning “to be high,” does not seem to give a satisfactory sense and so some change the Hebrew text to a verb meaning “increases.” This gives a better parallel with line 1. In either case the sense seems clear that a person with a quick temper acts foolishly or shows his lack of intelligence. Contemporary English Version says “It’s smart to be patient, but it’s stupid to lose your temper.” Biblia Dios Habla Hoy has “To be patient shows much intelligence; to be impatient shows great stupidity.”

Quoted with permission from Reyburn, William D. and Fry, Euan McG. A Handbook on Proverbs. (UBS Helps for Translators). New York: UBS, 2000. For this and other handbooks for translators see here .