THE LIGHT in his eyes was like a green flame as he sped back after the Hobbit to recover his precious.
Gollum finally realises Bilbo Baggins has the ring and comes after him. His screech alerts Bilbo to the danger and he starts to run. As he does so he puts his hand in his pocket and the ring slips onto his finger. The ring makes the wearer invisible and after some time Bilbo realises that Gollum can't see him. Gollum heads for the entrance of the tunnels where he is sure Bilbo will eventually turn up, Bilbo follows him and finds his way out. Bilbo has the opportunity to slay Gollum who can't see him, but at the last moment PITY STAYED HIM, HE WOULD NOT USE IT TO HELP HIM KILL THE WRETCHED CREATURE AT A DISADVANTAGE. He leaps over Gollum and escapes.
The Beatitudes are 10 important truths that Jesus taught. Number seven is: Blessed are the merciful for they shall obtain mercy. (Math 5v7).
Later in the book while Gandalph the wizard is explaining about the ring to Frodo, Frodo says,'what a pity Bilbo didn't stab that vile creature while he had the chance'. Gandalph replies, 'pity! It was pity that stayed his hand, pity and mercy: not to strike without need. And he has been well rewarded, Frodo. Be sure that he took so little hurt from the evil, and escaped in the end, because he began his ownership of the ring so. With pity!!'
Bilbo had ownership of the ring for many years, but it did not affect him with the same severity of evil as it did Gollum. Because of his mercy he obtained mercy. Many chapters further on Frodo himself is tempted to kill Gollum, who has attacked he and Sam on the trail, but Gandalphs words come back to his mind and he chooses not to slay Gollum. The book reveals that Frodos decision at that time is a major factor in his life being saved at the end of the journey. He was merciful and he obtained mercy.
Thus one of the spiritual truths that Jesus emphasised as of great importance, is used by Tolkien as one of the foundations of his story.