tāo guāng yǎng huì
to conceal one's strengths and bide one's time (idiom)
to hide one's light under a bushel
韬
tāo
bow case or scabbard
光
guāng
light; ray (CL:道[dao4])
养
yǎng
to raise (animals)
晦
huì
(bound form) last day of a lunar month