路遙知馬力，日久見人心。(元雜劇)
語意 : 說明時間可考驗一個人的內心是否善良。
出處 : 醒世恆言卷三五 明 馮夢龍
話說路遙和馬力是好朋友，路遙父親是富商，馬力的父親是路遙家的僕人。
雖然是主僕關係，兩人的關係很好。他們一起讀書，一起玩耍。
到了該談婚論嫁的年齡了，路遙有錢有勢，不愁老婆。而馬力貧困潦倒，一直沒人提親。
有一天有媒人給馬力提親，馬力大喜，但是卻要昂貴的彩禮。馬力只好請同學路遙幫助，路遙說﹕借錢可以，但是結婚入洞房我來替你前三天。
馬力怒火沖頭，但是又沒有辦法，總不能光棍一輩子，只好答應。于是選擇好日子結婚。
馬力煎熬過痛苦的三天，第四天該他洞房了，心裡懊呀！天一黑就一頭栽進洞房拉被蒙頭就睡覺。
新娘子就問：夫君，為何前三夜都是通宵讀書，今天卻矇頭大睡？馬力這才知道路遙給他開了個大玩笑，真實又喜又惱。被有錢的朋友給耍了。發誓好好讀書，考取它狀元。後來還真考上了並在京城做了大官。
路遙性情豪放，俠肝義膽，最後卻坐吃山空。看到自己一家實在無法度日，想起曾經資助的朋友馬力，於是就和老婆商量自己進京找他幫助。馬力見到路遙很是高興，熱情款待，路遙說明來意，
馬力卻說：喝酒！喝酒！根本沒有幫助他的意思，路遙很惱。
過了幾天，馬力說：路兄，你回家吧，免得嫂夫人牽掛！路遙只得氣憤沮喪的回家。還沒進家就聽見家裡哭成一片，急忙進來。
看到妻兒守著一口棺材痛哭，一見路遙進來家人又驚又喜。原來是馬力派人送來棺材說：路遙到京城後，生了重病，醫治無效而死！路遙更加惱怒，打開棺材一看裡面是金銀財物，
還有一紙條上寫：你讓我妻守三天空房，我讓你妻痛哭一場。
◎ 路遙知馬力、日久見人心。在你的生命中有多少這樣的朋友；在你需要幫忙的時候給予你最真誠的幫助！
- The story of Lu Yao and Ma Li
According Chinese folklore, Lu Yao (路遥) and Ma Li (马力) were good friends. Lu Yao, who was born in a rich family, helped Ma Li to find a maid and arranged their wedding party, but in return he demanded that he should spend the first three nights in the bride's room. With the alternative of having no wife at all, Ma Li was forced accepted this absurd demand. On the fourth night, Ma Li entered the bride's room, only to learn that Lu Yao actually slept in a separate room during the three nights. He just played a crue joke on him.
Time went by. Many years later, Ma Li, through his dilligence, bacome a powerful official while Lu spent away his family wealth. In destitude, he went to Ma Li for help. Ma Li treated him well, but didn't promise him of any financial help. After a few days, he asked Lu Yao to go home, empty-handed. Very disappointed, Lu Yao returned. When he was approaching his house, he heard his wife and relatives crying, and saw a coffin lying in the middle of the yard, with his wife crying for her dead husband. Bewildered, he asked his wife what happened and was told that a few days after he left for help, Ma Li sent his men with this coffin, saying that Lu Yao had died due to illness and exhaustion from the journey. Upon hearing this, Lu Yao angrily opened the coffin to see what trick Ma Li was playing, only to find it was full of gold bullions and precious stones, with a note saying '你教我妻守空房，我教你妻哭断肠’(you made my bride spend the first three nights alone, I would make your wife cry her heart out).
That's the story of Lu Yao and Ma Li, two good friends playing cruel jokes on each other.