The knight was angry and said he would never for that fail to kill him, and he raised his sword to strike. When Merlin saw that, he cast a spell, so that he made the knight fall asleep above Arthur.

Merlin picked the king up and said to him, “Now you may see that my knowledge is worth more to you than your prowess. I told you this morning that this would happen.”

The king stood up quickly and found the knight sleeping, not moving at all. He thought that the knight was dead and that Merlin had killed him by his spell, and he said quickly to Merlin, “Merlin, you have done ill in killing this knight; his loss will never be compensated, for in my opinion he was the best knight in the world. God willing, I would rather have lost the best castle I have than that you had killed him so.”

‘What?” asked Merlin; “do you think he is dead?”

“He seems so to me,” said the king.

“Know, then,” said Merlin, “that he is fully alive, and he won’t wake up until I choose.”

Post-Vulgate Merlin