放下屠刀，立地成佛

fàngxià túdāo, lìdì chéng fó

[drop one's cleaver and become a Buddha-a wrongdoer achieves salvation as soon as one gives up evil] 原为佛教禅宗劝人修行的话, 后用来比喻作恶的人只要决心悔改, 就会变成好人

从来说孽海茫茫, 回头是岸, 放下屠刀, 立地成佛。 --《儿女英雄传》