What is the smart donkey talking about?

When the King of Moavia went out for a walk, he saw a jingling bell hanging on the neck of a donkey that was grinding mills. He curiously asked the miller: "Why do you have to hang a bell on the donkey's neck?" "Where is the bell?"

The miller told the king: "If I turn my back and the bell stops ringing, I will know that it is lazy."

The king said: "What if the donkey does not go away, but only shakes its head, does not work, and lets you hear the bell ringing?"

"Ah, my wise majesty!" The miller He smiled and replied, "I never thought there would be such a smart donkey in the world."