Failure to equip.
In 1 Samuel 17:38-39 we see the failure of a leader to equip his follower. King Saul did not know David well; He did not know that David could not fight in this heavy armor. In fact Saul did not know David could fight at all; Saul stated, “You are not able to go against this Philistine to fight with him; for you are but a youth while he has been a warrior from his youth.” This highlights a few things about Saul’s failure to equip David. Firstly, Saul did not know David very well. He was unaware of David’s capabilities, sure David told Saul of some of his abilities, but outside of that information, Saul knew next to nothing; if he had known David’s capabilities, he would have known that the armor was useless to David.
Secondly, Saul was trying to export his own philosophy of war to David. David had never been in a military campaign; he was a youthful shepherd, not a warrior, at least not yet. Saul was trying to give him his own weapons of war that he had learned which David was unfamiliar with. David said it himself, “I cannot walk with these, for I have not tested them.”
Thirdly, Saul did not listen to David. David told Saul that he killed both a lion and a bear while defending his sheep. Apparently David had killed them with his bare hands, but Saul did not recognize this great feat. Saul was too caught up trying to abstain from entering the battle himself to listen. David was confident that God would deliver him, just as he had delivered him before.
Thus, Saul’s failure to equip David came from not knowing his follower, pushing his philosophy onto him, and not listening to him. This was a complete failure to equip David on Saul’s part. Had David been able to wear the armor and fight the way Saul wanted him to, he likely would have been killed if God did not intervene on his behalf. David knew his own strengths and weaknesses; he knew his best chance to defeat Goliath, was by using equipment he was familiar with—shepherd tools.