From Longman Dictionary of Contemporary Englishit won’t/wouldn’t kill somebody (to do something)it won’t/wouldn’t kill somebody (to do something)spoken used to say that someone could easily do something, and ought to do it It wouldn’t kill you to help out once in a while. → kill
Examples from the Corpus
it won’t/wouldn’t kill somebody (to do something)• It wouldn't kill you to do the dishes. 