"Preaching to the choir"
Hello! I am a silly American who needs a hand. So, something I say a lot is "preaching to the choir." I just used it in my hp fic draft and thought "oh, wait, is that something that would make sense to a wizard?" and then I realized that I wasn't even sure if it was used outside of the US. Google is kind of wishy-washy on the subject, so I thought I'd ask here. Thanks!