1 Samuel 17:47 - Joseph Benson’s Commentary on the Old and New Testaments

Saveth not with sword and spear That is, that he can save without these arms, and with the most contemptible weapons, and that he needs not human force to effect his designs. For the battle is the Lord's The events of war are wholly in his power. And he will give you into our hands David speaks thus confidently, because he was assured of success, by particular inspiration. How great is the difference between the speech of Goliath and that of David! The former consists of the vain- glorious boasting words of a man proudly confiding in his own strength, and thinking of nothing but his own glory. The words of the latter, although expressing an equal assurance of victory, are humble and modest, attributing nothing to himself, but all to the power and goodness of God; building his hopes upon, and rejoicing in, the honour that would accrue to God from his success, instead of puffing himself up with the glory that would arise to himself therefrom.