熟不讲礼

Traditional (Taiwan): 熟不講禮

shúbùjiǎnglǐ ㄕㄨˊ ㄅㄨˋ ㄐㄧㄤˇ ㄌㄧˇ

    • close friends needn't stand on ceremony

Character by character

Saying俗语俗語

Proverb谚语諺語 · Widely known

Literally
when familiar, don't stand on ceremony
Meaning
Close friends needn't be formal with each other. Said to put a familiar guest at ease or to excuse informality.

Sources