English equivalent of this Tamil saying [duplicate]

Question

There is a famous saying in Tamil language: "Paarthaal pasu pol, paaindhaal puli pol" which translates to "Looks like a cow, leaps like a tiger".

This is usually used to describe a person who on first look gives an impression that they are silent and submissive, but when confronted, they dominate the confronter.

The closest English proverb which I could think of is Appearances are deceptive, but it doesn't essentially capture the silent nature and the combative nature of a person.

Is there an English saying which means the same?

Answer 1

There is of course the expression of the wolf in sheep's clothing, which is of biblical origin:

A Wolf in sheep's clothing is an idiom of Biblical origin used to describe those playing a role contrary to their real character with whom contact is dangerous, particularly false teachers.