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.
Books of Samuel
One of the main units within Samuel is the "History of David's Rise", the purpose of which is to justify David as the legitimate successor to Saul. The narrative stresses that he gained the throne lawfully, always respecting "the Lord's anointed" (i.e. Saul) and never taking any of his numerous chances to seize the throne by violence. As God's chosen king over Israel, David is also the son of God ("I will be a father to him, and he shall be a son to me..." – 2 Samuel 7:14). God enters into an eternal covenant (treaty) with David and his line, promising divine protection of the dynasty and of Jerusalem through all time.