狗咬吕洞宾，不识好人心

狗咬呂洞賓，不識好人心
gǒuyǎo Lǚ Dòngbīn,bùshíhǎorénxīn
  1. a dog biting Lü Dongbin (idiom)
  2. to ill reward a person's kindness

CEDICT

Entry Composition

1 狗咬吕洞宾 gǒuyǎo Lǚ Dòngbīn short for 狗咬呂洞賓——不識好人心／狗咬吕洞宾——不识好人心 (gǒu yǎo Lǚ Dòngbīn, bùshí hǎorén xīn, “to bite the hand that feeds you”)
2 不识 bùshí
  1. (literary) to fail to see; not to know; not to appreciate
  2. to fail to see; not to know; not to appreciate
3 好人 hǎorén
  1. good person
  2. healthy person
  3. person who tries not to offend anyone, even at the expense of principle
4 心 xīn
  1. heart
  2. mind
  3. intention
  4. center
  5. core

classifiers: 顆, 個