1 Samuel 17:9 - Ellicott's Commentary On The Whole Bible

Then will we be your servants. — Each of the positions which the two opposing armies held was well-nigh impregnable; thus it seemed as though a single combat was the only way of deciding the present campaign: besides which, in those far back times such single combats between renowned chieftains of the opposing armies were not by any means uncommon. The reader of the Iliad will ever readily call to mind — in colloquies before the deadly duel — words not altogether unlike the haughty, boastful challenge of the giant Philistine. See, for instance, the speeches of Glaucus and Diomede in Book VI. of the Iliad: “Come hither,” says Glaucus, “that you may quickly reach the goal of death.”