So David prevailed over the Philistine with a sling and with a stone, and struck the Philistine and killed him. There was no sword in the hand of David. 1 Samuel 17:50
David used what he was skilled in to defeat his enemy. King Saul tried to arm David with his armor, and encouraged David to fight like a soldier. Often people with expertise in a certain area will try to get us to do things their way. Just because someone else has had success doing it their way does not mean that is God’s way for us. We need to use our specific talents and skills to serve God in the area he calls us. It is wise to see how those who have gone before us have done things. It is not wise to try to be like someone else. Often we look only to the lessons from others rather than following God. Under no normal circumstance could a shepherd boy defeat an experienced soldier with a sling. This would be foolishness to anyone experienced with fighting battles. But God is always doing new things. We need not to limit ourselves to the knowledge of men. Jesus looked at them and said, “With man it is impossible, but not with God. For all things are possible with God” Mark 10:27.