家醜不可外傳，流言切莫輕信 [－丑－－－传－－－－－轻－]

Jyutping gaa1 cau2 bat1 ho2 ngoi6 cyun4 , lau4 jin4 cit3 mok6 hing1 seon3
Pinyin jiā chǒu bù kě wài chuán , liú yán qiè mò qīng xìn

Definitions (CC-CEDICT)
  1. Don't spread abroad the shame of the family, don't believe rumors lightly. (idiom)
  2. Don't wash your dirty linen in public, don't listen to others' gossip.