‘Deshan said to the monks, “As soon as you ask, you have erred. If you don’t ask, you’re also wrong.”
A monk came forward and bowed. Deshan struck him.
The monk said, “I just bowed. Why did you hit me?”
Deshan said, “What use would it be to wait until you opened your mouth?”‘ (Zen’s Chinese Heritage)
The monk thought he was being clever, but having been hit, he should have just bowed again to his master.