能ある鷹は爪を隠す (のうあるたかはつめをかくす): a wise man keeps some of his talents in reserve; one shouldn't show off; the person who knows most often says least

a wise man keeps some of his talents in reserve; one shouldn't show off; the person who knows most often says least

The capable hawk keeps its talons out of sight. Praise for someone who never mentioned what they could do until it mattered, and a quiet rebuke to anyone doing the opposite.