Arthur needs healing

Bedivere goes to do so, then decides to keep Excalibur for himself, so he tells Arthur he did it, and Arthur asked what he saw in the lake. Bedivere goes "Um...waves? rocks? That kind of thing?" and Arthur backhands him, which HURTS despite Arthur having his cap peeled back and his grey matter on his scalp. "Go back, and actually return the sword."
Repeat the same exchange, including the backhand and the third time, Bedivere succeeds. The Lady of the Lake raises the sword into the light, then disappears. Bedivere heads back, only to see three women stealing Arthur's barely conscious body. One of them lowers her hood to reveal she’s Morgana le Fae. She looks back and yells at Bedivere "We're taking Arthur to Avalon to be healed. He'll be back.... you know, someday. Probably when England most needs him."

Arthurian Myths Retold Pg 201