Synopsis of the Books of the Bible, by John Nelson Darby, [1857-62], at sacred-texts.com
The Philistines, that type of the enemy's power, present themselves again with their champion at their head, against whom no one dares to fight. David had returned home, and was living in the simplicity of his usual life. Although that which precedes gives the general idea of the position in which he had been placed, it appears that David had not remained long with the king (Sa1 17:15). His father sends him to see his brothers, who are in Saul's army. There he sees the Philistine who defied the armies of Israel. Jonathan does not appear here. There is but one who can destroy this champion, who centres in his own person all the energy of evil. David's faith sees no difficulty in it because he sees God, and in the enemy an enemy of God without strength. He was but one of the "uncircumcised"; the rest matters little. In the performance of his ordinary duties David had already met with difficulties too great for a full-grown man; yet, although a mere youth, he had overcome them for a very simple reason-"Jehovah delivered." He had not boasted of this (it was the fulfilment of his duty); but he had learnt in it the strength and faithfulness of Jehovah. And this experience is now repeated. Man's armour is rejected; faith knows it not. God will perform the work by the most simple means.
David declares wherein his strength consists. "I come to thee in the name of Jehovah of hosts." He then identifies himself with the people of God. "All the earth shall know that there is a God in Israel." Remark how the simplicity of faith rises to the consciousness of power and its effects in the hands of God (Sa1 17:46). So ever when God leads the heart. The stone which sinks into the forehead of Goliath deprives him of strength and of life. David cuts off the head of Goliath with his own sword, like Him who by death destroyed him that had the power of death.
The whole army of Israel profits by David's triumph. Saul, who had forgotten him, will not suffer him to go away. Alas! the flesh, and even the flesh in rebellion, can love Jehovah's elect on account of his kindness and the relief he ministers; but it knows him not. When he is doing Jehovah's work, he is as much a stranger to Saul as if they had never met.