Cease ye from man, whose breath is in his nostrils: for wherein is he to be accounted of? Isaiah 2:22
“His breath is in his nostrils” is an Aramaic idiom which means that he is impatient, hasty, or impulsive; this refers to a person who does not think things over, but acts without thinking. [We would call this person a "hothead."]
This idiom is still used among Aramaic-speaking people. When a man is hasty or impatient he talks with his breath in his nostrils. [Angry men have flared nostrils also.] Easterners consider impatient men dangerous. Leaders and judges who are impulsive are greatly feared and are considered impractical. Easterners generally think things over before they act, especially the wise men. They let a matter cool off for a while before they make a decision.
(Lamsa, George M. 1964. Old Testament Light. San Francisco: Harper Collins., pgs 620-621)