Drop the subject!

Drop the subject!

 and Drop it!
Fig. Do not discuss it further! Bill: Sally, you're gaining a little weight. I thought you were on a diet. Sally: That's enough! Drop the subject! Bill: That house is a mess. I wonder who lives there. Mary: That's my aunt's house. Just what did you want to know about it? Bill: Oh, drop it! Sorry I asked.
See also: drop