Waste your breath
Meaning: Speak uselessly, to no purpose. If you waste your breath, you spend time and energy trying to give advice that is ignored.
Example: Honestly, you're wasting your breath - he doesn't want to hear what anyone else has got to say. Don’t waste your breath trying to make him do it, he won’t change his mind.
Example: Honestly, you're wasting your breath - he doesn't want to hear what anyone else has got to say. Don’t waste your breath trying to make him do it, he won’t change his mind.