入rù乡xiāng随suí俗sú

Literal: enter the village, follow its customs
Figurative: When you arrive somewhere new, adapt to the local customs rather than imposing your own; when in Rome, do as the Romans do.

Where does 入乡随俗 come from?

It is a proverbial saying rather than a specific story. The notion of learning the customs of a place you visit appears already in the 《礼记》 with phrases such as 入国问俗 ("on entering a country, ask about its customs"). The fixed four-character form 入乡随俗 is recorded in the Song-era Buddhist Chan text 《五灯会元》, and it has since been used to advise adapting respectfully to one's surroundings.

Source (出处): 《五灯会元》

How is 入乡随俗 used? Two examples

既jì然rán来lái了le这zhè里lǐ，我wǒ们men就jiù入rù乡xiāng随suí俗sú，跟gēn大dà家jiā一yī样yàng用yòng手shǒu吃chī饭fàn吧ba。
Since we've come here, let's do as the locals do and eat with our hands like everyone else.
在zài国guó外wài读dú书shū要yào学xué会huì入rù乡xiāng随suí俗sú，多duō了liǎo解jiě当dāng地dì的de生shēng活huó习xí惯guàn。
Studying abroad means learning to adapt to local customs and getting to know the area's way of life.

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