一寸光阴一寸金，寸金难买寸光阴
yī​cùn​guāng​yīn​yī​cùn​jīn, cùn​jīn​nán​mǎi​cùn​guāng​yīn

time is precious

一寸光阴一寸金，寸金难买寸光阴 (一寸光陰一寸金，寸金難買寸光陰) yī​cùn​guāng​yīn​yī​cùn​jīn, cùn​jīn​nán​mǎi​cùn​guāng​yīn
time is precious
an interval of time is worth an ounce of gold and money cannot buy it back; used to emphasize that time is invaluable

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CC-CEDICT