The three wise monkeys (Japanese: 三猿, san'en or sanzaru, or 三匹の猿, sanbiki no saru, literally "three monkeys") are a pictorial maxim. Together they embody the proverbial principle to "see no evil, hear no evil, speak no evil". The three monkeys are Mizaru, covering his eyes, who sees no evil; Kikazaru, covering his ears, who hears no evil; and Iwazaru, covering his mouth, who speaks no evil.
Sometimes there is a fourth monkey depicted with the three others; the last one, Shizaru, symbolizes the principle of "do no evil". He may be covering his abdomen or crotch, or just crossing his arms.
In Chinese, a similar phrase exists in the Analects of Confucius: "Look not at what is contrary to propriety; listen not to what is contrary to propriety; speak not what is contrary to propriety; make no movement which is contrary to propriety" (非禮勿視， 非禮勿聽，非禮勿言， 非禮勿動). It may be that this phrase was shortened and simplified after it was brought into Japan. (more here at Wikipedia)
I practiced "Hear No Evil, See No Evil, Speak No Evil, Do No Evil", until I discovered Psychology as a teen, and learned to "free my spirit" through uncensored expression of all the evil I saw in my present and in my past. Eventually I discovered the evil in me - which brought me right back to getting more quiet about it all. Eric Clapton's "Before You Accuse Me" comes to mind - or Jesus with the splinter/log advice.
When it comes to punishment of evil, defending ourselves, or protecting ourselves against it, we need to be aware that we are trying to defend ourselves against those who make us afraid. Once we truly realize that there is no evil and with that realization lose our fear - particularly our fear of death - we can act with far more wisdom, compassion, justice and practicality.