Your servant struck both the lion and the bear: and this uncircumcised Philistine shall be as one of them, seeing he has defied the armies of the living God.
Some students of this passage have suggested that David chose five stones because Goliath had four brothers, and he wanted to be ready to attack them too. However there is no indication in the text that David had any concern for them or even that they were present at this battle. He probably chose five stones simply so he would have some in reserve if his first shot missed its mark.