Three times in the chronicles of Narnia, Lewis describes a character cleaning or drying his sword. In none of them is it necessary to the rest of the plot.

_The Lion, The Witch and the Wardrobe_:
> Peter, still out of breath, turned and saw Aslan close at hand.

> "You have forgotten to clean your sword," said Aslan.

> It was true. Peter blushed when he looked at the bright blade and saw it all smeared with the Wolf's hair and blood. He stooped down and wiped it quite clean on the grass, and then wiped it quite dry on his coat.

> "Hand it to me and kneel, Son of Adam," said Aslan. And when Peter had done so he struck him with the flat of the blade and said, "Rise up, Sir Peter Wolf's-Bane. And, whatever happens, never forget to wipe your sword."

_The Last Battle_:
>  The King was still so angry that he hardly noticed the cold of the water. But of course he dried his sword very carefully on the shoulder of his cloak, which was the only dry part of him, as soon as they came to shore.

Also _The Last Battle_:
> Then he inspected Eustace's sword and found that Eustace had put it back in the sheath all messy from killing the Calormene. He was scolded for that and made to clean and polish it.

(All the quotations are from copies I found on the Web and may be somewhat inaccurate.)

Why did Lewis include these? Why the obsession with this topic?

(Of course, many aspects of the Narnia stories are an analogy to concepts in Christianity; perhaps this is one such? Does Christianity attach some especial value to clean, dry swords, or to something analogous?)