Goliath
Goliath is described in the biblical Book of Samuel as a Philistine giant defeated by the young David in single combat. The story signified Saul's unfitness to rule, as Saul himself should have fought for the Kingdom of Israel.
Saul
After Samuel tells Saul that God has rejected him as king, David, a son of Jesse, from the tribe of Judah, enters the story: from this point on Saul's story is largely the account of his increasingly troubled relationship with David.Saul offered his elder daughter Merab as a wife to the now popular David, after his victory over Goliath, but David demurred. David distinguishes himself in the Philistine wars. Upon David's return from battle, the women praise him in song:
implying that David is the greater warrior. Saul fears David's growing popularity and henceforth views him as a rival to the throne.