This expression came to us from the East, or rather from Buddhism. It is associated with three wise monkeys, one of whom closes his eyes (I see nothing), the other ears (I hear nothing) and another mouth "I will not tell anyone."
The meaning of the phrase is that in order to protect yourself from evil, you need to renounce it - "If I do not see evil, do not hear about evil and do not say anything about it, then I am protected from it." Sometimes a fourth monkey is added - Sezaru, symbolizing the principle of "not committing evil." She can be depicted covering her belly or crotch.
The choice of monkeys as a symbol is associated with pun in Japanese. The phrase “I don't see anything, I don't hear anything, I don't say anything” sounds like “mizaru, kikazaru, ivazaru”, the ending “dzaru” is consonant with the Japanese word “monkey”.
In the west, "Three Monkeys" have become popular since the 17th century thanks to the sculpture above the doors of the famous Shinto shrine of Toshogu in the Japanese city of Nikko.
A similar phrase is found in the book of Confucius "Lun Yu" (China): "Don't look at what's wrong; Don't listen to what's wrong; Don't say what's wrong; Don't do what is wrong. "