Proverbs 29:11

A fool uttereth all his mind: but a wise man keepeth it in till afterwards.
– Proverbs 29:11

The first phrase literally says a fool vents all his breath. The picture is such a sheer quantity of words coming from a fool he is out of breath. Fools are characterized in Proverbs for much foolish speaking. They pour out words like water from a bucket (Proverbs 15:2, 28). It is such a common indicator that a fool might be thought wise by simply being quiet and offering no opinion (Proverbs 17:28).

A fool’s speech is not marked only by quantity, but also by content, all his mind. A fool is compelled to make his foolishness known (Proverbs 12:32; 13:16; 14:33). Such characteristic speaking is a product of the lack of self-control, particularly in terms of anger (Proverbs 12:16).

Most of the verses referenced have the contrasting characteristic of the wise that he has control over his tongue. The wise will understand many reasons for restraining speech: provide less to be used against him (Proverbs 10:14; 13:3), maintain relationships (Proverbs 11:12-13), calm heated tempers (Proverbs 17:27; 15:1), and even to lessen sin (Proverbs 10:19).

That a wise man keeps his words in till afterwards, can provide a cooling off period until minds are more reasonable, but also speaks to the characteristic wisdom of taking time to investigate, understand, and formulate a reasonable response (Proverbs 15:28; 18:13, 17).