人不可貌相狗不可斗量
[rén bù kĕ mào xiāng gŏu bù kĕ dòu liàng]
The direct translation is 'Don't judge a book by its cover for people and you cannot estimate the amount of food a dog can eat by just looking'. It means that appearances can be deceiving and it's important not to make snap judgments about a person based on external appearances. This saying reflects wisdom and understanding in Chinese culture.