Why will Beowulf challenge Grendel without the use of a sword in Beowulf?

There are several reasons why Beowulf wants to fight
Grendel without the use of a sword. His famous "boasts" of bravery in battle is one
reason-he wants people to talk about it like they have talked about his other conquests.
For instance, he loves the fact that Wiglaf has talked about his fight with the dragon
under water and the fact that his speech backfires on him. He also wants to prove it to
himself that he can do it. I think there is part of him that wants to fight Grendel
fairly. Grendel has no weapons, so he wants to meet him on his terms, as seen
below:

"Of
force in fight no feebler I count me,
in grim war-deeds, than Grendel deems
him.
Not with the sword, then, to sleep of death
his life will I
give, though it lie in my power.
No skill is his to strike against
me,
my shield to hew though he hardy be,
bold in battle; we both,
this night,
shall spurn the sword, if he seek me here,
unweaponed,
for war. Let wisest God,
sacred Lord, on which side soever
doom
decree as he deemeth
right."

He wants to battle
Grendel "unweaponed" because Grendel cannot help but "spurn the sword." The final reason
is illustrated in the last line of this passage: "Let wisest God, sacred Lord, on which
side soever doom decree as he deemeth right." Beowulf trusts on God to help the
righteous winner win.