The Lion, the Witch, and the Wardrobe
How we cite our quotes:
But amidst all these rejoicings Aslan himself quietly slipped away. And when the Kings and Queens noticed that he wasn't there they said nothing about it. For Mr. Beaver had warned them, "He'll be coming and going" he had said. "One day you'll see him and another you won't. He doesn't like being tied down – and of course he has other countries to attend to. It's quite all right. He'll often drop in. Only you mustn't press him. He's wild, you know. Not like a tame lion." (17.23)
Aslan's ways are not the ways of men (or Narnian creatures), and there will always be something inexplicable and mysterious about him. He can't be tied down to a regular schedule and he won't ever do things in quite the way you expected.