1. 1 Samuel 17:51 (ESV)
  2. Exposition

Why did David cut off Goliath’s head?

1 Samuel 17:51 (ESV)

51 Then David ran and stood over the Philistine and took his sword and drew it out of its sheath and killed him and cut off his head with it. When the Philistines saw that their champion was dead, they fled.

Cutting off Goliath's head, David most probably lifted it high for the Philistine army to see, so that they could know their champion was defeated.