The Wizard and the Hopping Pot?

"Tch," Autor says. "We've used too many words in this conversation already. Eat your food; as long as your mouth is full, you won't be speaking."

It's only after he says the words does he feel a pang of regret: Lohengrin had said the same to Autor, so very long ago. Specifically after Autor had congratulated the Knight on his wedding.