Answer:
out of pride.
Step-by-step explanation:
In Lines 1492-1650, Beowulf fights with Grendel's mother, ultimately severing her head from the body. After beheading her, light shines in the cave uncovering the corpse of Grendel. Furious, Beowulf cuts off the head of Grendel.
On seeing the blood well springing out Danes thinks that Beowulf had lost and went back to Heorot. But the geats, kinsmen of Beowulf waits for him.
When Beowulf returns to the land, his kinsmen seeing him alive and with the head of Grendel rejoiced. The Geats went back to the hall of Heorot with the head of Grendel. The head of Grendel was so heavy that it took four men to carry his head. Geats carried the heavy head of Grendel back to Heorot hall out pride, as a trophy.