水shuǐ滴dī石shí穿chuān

Literal: water drips, the stone is pierced
Figurative: Small but steady effort ends up achieving what seemed impossible; the stress is on something tiny, repeated over a long time.

Where does 水滴石穿 come from?

It is recorded in 《鹤林玉露》 by Luo Dajing (Song dynasty). When Zhang Yong (Zhang Guaiya) was magistrate of Chongyang, he saw a clerk leaving the storehouse with a coin tucked under his headcloth and ordered him flogged. The clerk protested that one coin was nothing, and that they could beat him but not put him to death. Zhang wrote in his verdict: "One coin a day, a thousand coins in a thousand days; a rope saws through wood, dripping water pierces stone," and executed him himself. In the story the line condemns harm that adds up; today it is used positively, for steady effort in small things.

Source (出处): 罗大经《鹤林玉露》

How is 水滴石穿 used? Two examples

每měi天tiān背bèi十shí个ge单dān词cí看kàn着zhe不bù多duō，可kě水shuǐ滴dī石shí穿chuān，一yī年nián后hòu我wǒ已yǐ经jīng能néng读dú懂dǒng小xiǎo说shuō了le。
Ten words a day doesn't sound like much, but constant dripping wears away stone: a year later I could already read novels.
他tā坚jiān持chí每měi周zhōu给gěi客kè户hù打dǎ一yī次cì电diàn话huà，水shuǐ滴dī石shí穿chuān，半bàn年nián后hòu终zhōng于yú签qiān下xià了le订dìng单dān。
He called the client once a week without fail, and, like water wearing away stone, six months later he finally landed the order.

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