The Lion and the Stream by C. S. Lewis
“Are you not thirsty?” said the Lion. “I’m dying of thirst,” said Jill. “Then drink,” said the Lion. “May I - could I - would you mind going away while I do?” said Jill. The Lion answered this only by a look and a very low growl. And as Jill gazed into its motionless bulk, she realized that she might as well have asked the whole mountain...