What does 1 Samuel 17:31 mean?
Saul knew David. David had been serving the king as a musician and even as his armor bearer (1 Samuel 16:14–23). David had been routinely traveling back and forth between serving Saul and caring for the sheep back home in Bethlehem (1 Samuel 17:15).Now the Israelites are at war with the Philistines (1 Samuel 17:1–3, 19), and David has come to the battle to deliver food for his brothers (1 Samuel 17:17–18). The Philistine champion, Goliath (1 Samuel 17:4–7), has challenged Israel to a representative fight (1 Samuel 17:8–10). If one of their soldiers could kill Goliath, the Philistines would serve Israel. If Goliath won, the Israelites would serve the Philistines. Goliath taunts the Israelites for forty days (1 Samuel 17:16), and the Israelites have responded in fear (1 Samuel 17:11, 24). But David has now heard Goliath's defiant challenge and taunts for the first time (1 Samuel 17:23). He has been outraged, asking what the king will do for the man who kills the giant who is bringing reproach on the armies of the living God (1 Samuel 17:26), even suggesting by the question that he could kill Goliath.
People who hear Jesse's youngest son declaring that Goliath can be beaten eventually report to Saul what they have heard David say. Saul is apparently so desperate for a solution to this standoff with the Philistines that he sends for the youth to ask him about what he has said.