expression, godan verb (-ru)
fail to prepare in time; not dig a well until one is thirsty
A classical proverb warning against procrastination: one should prepare before a need arises. The literal meaning is 'to dig a well when one is thirsty.' Often used to criticize lack of foresight.
渇に臨みて井を掘るでは遅すぎる。
It's too late to dig a well when you're already thirsty.
He's always doing things like digging a well only after he gets thirsty.