48 That roused the Philistine, and he started toward David. David took off from the front line, running toward the Philistine. 49 David reached into his pocket for a stone, slung it, and hit the Philistine hard in the forehead, embedding the stone deeply. The Philistine crashed, facedown in the dirt. 50 That's how David beat the Philistine - with a sling and a stone. He hit him and killed him. No sword for David! 51 Then David ran up to the Philistine and stood over him, pulled the giant's sword from its sheath, and finished the job by cutting off his head. When the Philistines saw that their great champion was dead, they scattered, running for their lives.
Matthew Henry's Commentary on 1 Samuel 17:48-51
Commentary on 1 Samuel 17:48-58
(Read 1 Samuel 17:48-58)
See how frail and uncertain life is, even when a man thinks himself best fortified; how quickly, how easily, and by how small a matter, the passage may be opened for life to go out, and death to enter! Let not the strong man glory in his strength, nor the armed man in his armour. God resists the proud, and pours contempt on those who defy him and his people. No one ever hardened his heart against God and prospered. The history is recorded, that all may exert themselves for the honour of God, and the support of his cause, with bold and unshaken reliance on him. There is one conflict in which all the followers of the Lamb are, and must be engaged; one enemy, more formidable than Goliath, still challenges the armies of Israel. But "resist the devil, and he will flee from you." Go forth to battle with the faith of David, and the powers of darkness shall not stand against you. But how often is the Christian foiled through an evil heart of unbelief!