口は災いの門
also: くちはわざわいのもん
Meanings
1
words can lead to disaster; the tongue is the root of calamities
Proverb warning that careless speech invites trouble. Often used as a caution against gossip or thoughtless remarks. Compare with 口は災いの元 (same meaning).
See also: 口は災いの元
They say the mouth is the gate of calamity, so you'd better not say unnecessary things.
He's the kind of person who really lives out the proverb 'the mouth is the gate of calamity.'