beat a dead horseidiom
Definition of beat a dead horse
chiefly US, informal
1 : to keep talking about a subject that has already been discussed or decided I don't mean to beat a dead horse, but I still don't understand what happened.
2 : to waste time and effort trying to do something that is impossible Is it just beating a dead horse to ask for another recount of the votes?
What did you just call me?! A Quiz