knock it off
knock it off {v. phr.}, {slang}, {informal}
1. To stop talking about something considered not appropriate or nonsensical by the listener. — Used frequently as an imperative.
Come on, Joe, knock it off, you're not making any sense at all!
2. To cease doing something; to quit. — Heavily favored in the imperative.
Come on boys, knock it off, you're breaking the furniture in my room!
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Source: A Dictionary of American Idioms