The Voyage of the Dawn Treader
"Dearest," said Aslan very gently, "you and your brother will never come back to Narnia."
"Oh, Aslan!" said Edmund and Lucy both together in despairing voices.
"You are too old, children," said Aslan, "and you must begin to come close to your own world now." (16.70-72)
"But there I have another name. You must learn to know me by that name. This was the very reason why you were brought to Narnia, that by knowing me here for a little, you may know me better there." (16.76)