Proverbs 29:11 in the King James Version
A fool uttereth all his mind: but a wise man keepeth it in till afterwards.
Context
10 The bloodthirsty hate a man of integrity; and they seek the life of the upright.
11 A fool vents all of his anger, but a wise man brings himself under control.
12 If a ruler listens to lies, all of his officials are wicked.