落井下石

jué bù néng luò jǐng xià shí

决不能落井下石。

Never take advantage of a person's misfortune.

xiàng yī gè gāng gāng shī yè de rén tǎo zhài děng yú luò jǐng xià shí

向一个刚刚失业的人讨债等于落井下石。

To demand money from a person who has just lost his job is hitting a man who is down.