In the pages 141-171, Beowulf had shown his intention to slay Grendel. Beowulf may have been fatherless in an early, but he had grown to be a brave warrior. He was also boastful and had bragged that he can kill any creatures, even the ones that seemed to be impossible to defeat.
Beowulf's speech in lines 141-175 serves two purposes, on the first hand, it reasons why Grendel must be slayed, why ridding the world of the monster is just and even necessary. This also helps portray Beowulf not just as a brave, fearless powerful warrior, but as a prudent and fair man as well.
