Which detail from The Hobbit best helps to develop the theme that friendship is more important than treasure?

The eagles come to the aid of the men, dwarves, and elves even though they do not usually get involved in the world outside of their own.

Bilbo gives the Arkenstone to Bard to help the dwarves and men settle their dispute.

Thorin comes to the aid of his friends, the men, showing that he can forget his stubborn resentments to defend his former companions.

Thorin refuses to share any treasure with the men, who are his friends, displaying an almost disgusting greed.

The Hobbit is a fantasy novel written by J. R. R. Tolkien. It follows the adventures of a hobbit named Bilbo Baggins, who goes on a journey to win a share of the treasure guarded by Smaug the dragon. He is accompanied by a band of dwarves led by Thorin.

At one point, Bilbo finds the Arkenstone, an heirloom of Thorin's family, and hides it away. The Wood-elves and Lake-men who aided the dwarves in their battles demand a share of the treasure, which Thorin refuses. Bilbo tries to offer them the Arkenstone to maintain peace, but Thorin is enraged, feeling betrayed. However, in the end, Thorin comes to the aid of his friends, showing that he can forget his stubborn resentments to defend his former companions. He is fatally wounded in the Battle of Five Armies but reconciles with Bilbo before dying.

This is why the third option is the correct one.