Answer
When David made the claim, “The battle is the Lord’s” in 1 Samuel 17:47, he likely was thinking about passages such as Deuteronomy 20:1. Within the book of Deuteronomy, the Lord gives the law to His people Israel through Moses. This law was part of a covenant relationship that provided Israel with a way to live before a holy God, relating to Him in obedience. This involved rules for living and covered topics such as warfare, found in Deuteronomy 20.
Deuteronomy 20 begins with a foundational principle for warfare—the God who delivered Israel from one of the most powerful nations in the known world, Egypt, was with them. He was the source of their strength, and just as He miraculously delivered Israel from the hands of Egypt, He could and would continue to deliver them from the hands of their adversaries.
First Samuel 17:31–58 is the account of David and Goliath. The adversaries of Israel were the Philistines (1 Samuel 17:1–3) and, more specifically, Goliath (1 Samuel 17:4). Goliath was a giant, measuring about 9 feet tall and fully girded with armor (1 Samuel 17:4–7). Goliath appeared before the army of Israel and challenged them to a one-on-one duel that would result in the defeat of the entire army of the losing opponent. This challenge resulted in fear for the people of Israel (1 Samuel 17:11)—all except for David.
David was a sheepherder, the youngest of his family and a non-participant in battle. David was only present on the battlefield because he had delivered food to his three oldest brothers. Upon arriving, David had realized what was taking place—Israel was standing in fear of an opposing army. At this realization, David asks the right question, “Who is this uncircumcised Philistine that he should defy the armies of the living God?” (1 Samuel 17:26). David volunteers to be the one to fight Goliath—a young sheepherder against a giant warrior.
Naturally, the people of Israel were resistant, including King Saul (1 Samuel 17:33). If David were to lose the battle, all of Israel would become servants of the Philistines. David argues his case, relating his success in fighting both a lion and a bear. Significantly, David does not mention his own strength against these animals but instead points to God’s power that will result in Goliath being like the lion and the bear—namely, defeated. Because Goliath has opposed the army of God, God would defeat him, and David would be successful in battle.
Interestingly, in 1 Samuel 17:43, Goliath curses David by his gods. In the Hebrew, the verb meaning “to curse” is in the Piel stem, making it declarative. The root of the word points to the state of being “insignificant.” Goliath was declaring that David was insignificant because of his stature and age.
David’s response to this declaration is found in 1 Samuel 17:45–47. David declares that the source of his power is the God of Israel. David uses a phrase translated as “the name of the Lord.” This phrase can be talking simply about the formal name of a person (namely, God). However, it often carries the idea of the source, being, and power of the Lord. This seems to be the way in which David is utilizing it.
When David says, “For the battle is the Lord’s” in 1 Samuel 17:47, he is drawing from promises found within the Mosaic Law (Deuteronomy 20:1) and is claiming that God is the source of power who determines the outcome of the battle—which David believes is victory for himself. As Samuel records, David is correct (1 Samuel 17:50). God used the physically weakest of the family of Jesse to display His might before the world. God maintains this pattern of utilizing the weak to shame the strong of the world, displaying His might and bringing Himself glory (1 Corinthians 1:27).
