一寸光阴一寸金

yī cùn guāng yīn yī cùn jīn lit. An interval of time is worth an ounce of gold. (idiom); fig. free time is to be treasured

， 寸金难买寸光阴

cùn jīn nán mǎi cùn guāng yīn An ounce of gold can't buy you an interval of time (idiom); Money can't buy you time.; Time is precious.