48 And it came to pass, when the Philistine arose, and came and advanced to meet David, that David hasted, and ran towards the ranks to meet the Philistine. 49 And David put his hand into the bag, and took thence a stone, and slang it, and smote the Philistine in his forehead, and the stone sank into his forehead; and he fell on his face to the earth. 50 So David overcame the Philistine with a sling and a stone, and smote the Philistine and killed him; and there was no sword in the hand of David. 51 And David ran, and stood upon the Philistine, and took his sword, and drew it out of its sheath, and killed him completely, and cut off his head with it. And when the Philistines saw that their hero was dead, they fled.
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!