20 So David left the sheep with another shepherd and set out early the next morning with the gifts, as Jesse had directed him. He arrived at the camp just as the Israelite army was leaving for the battlefield with shouts and battle cries. 21 Soon the Israelite and Philistine forces stood facing each other, army against army. 22 David left his things with the keeper of supplies and hurried out to the ranks to greet his brothers. 23 As he was talking with them, Goliath, the Philistine champion from Gath, came out from the Philistine ranks. Then David heard him shout his usual taunt to the army of Israel. 24 As soon as the Israelite army saw him, they began to run away in fright. 25 "Have you seen the giant?" the men asked. "He comes out each day to defy Israel. The king has offered a huge reward to anyone who kills him. He will give that man one of his daughters for a wife, and the man's entire family will be exempted from paying taxes!" 26 David asked the soldiers standing nearby, "What will a man get for killing this Philistine and ending his defiance of Israel? Who is this pagan Philistine anyway, that he is allowed to defy the armies of the living God?"
Matthew Henry's Commentary on 1 Samuel 17:20-26
Commentary on 1 Samuel 17:12-30
(Read 1 Samuel 17:12-30)
Jesse little thought of sending his son to the army at that critical juncture; but the wise God orders actions and affairs, so as to serve his designs. In times of general formality and lukewarmness, every degree of zeal which implies readiness to go further, or to venture more in the cause of God than others, will be blamed as pride and ambition, and by none more than by near relations, like Eliab, or negligent superiors. It was a trial of David's meekness, patience, and constancy. He had right and reason on his side, and did not render railing for railing; with a soft answer he turned away his brother's wrath. This conquest of his own passion was more honourable than that of Goliath. Those who undertake great and public services, must not think it strange if they are spoken ill of, and opposed by those from whom they expect support and assistance. They must humbly go on with their work, in the face not only of enemies' threats, but of friends' slights and suspicions.