韬光养晦

tāo guāng yǎng huì

to conceal one's strengths and bide one's time (idiom)

to hide one's light under a bushel

tāo

bow case or scabbard

guāng

light; ray (CL:道[dao4])

yǎng

to raise (animals)

huì

(bound form) last day of a lunar month