Flavius Josephus, Antiquities of the Jews
William Whiston, A.M., Ed.

[184] However, Saul prayed that the end might be, by God's assistance, not disagreeable to the alacrity and boldness of the child; and said, "Go thy way to the fight." So he put about him his breastplate, and girded on his sword, and fitted the helmet to his head, and sent him away. But David was burdened with his armor, for he had not been exercised to it, nor had he learned to walk with it; so he said, "Let this armor be thine, O king, who art able to bear it; but give me leave to fight as thy servant, and as I myself desire." Accordingly he laid by the armor, and taking his staff with him, and putting five stones out of the brook into a shepherd's bag, and having a sling in his right hand, he went towards Goliath. But the adversary seeing him come in such a manner, disdained him, and jested upon him, as if he had not such weapons with him as are usual when one man fights against another, but such as are used in driving away and avoiding of dogs; and said, "Dost thou take me not for a man, but a dog?" To which he replied, "No, not for a dog, but for a creature worse than a dog." This provoked Goliath to anger, who thereupon cursed him by the name of God, and threatened to give his flesh to the beasts of the earth, and to the fowls of the air, to be torn in pieces by them. To whom David answered, "Thou comest to me with a sword, and with a spear, and with a breastplate; but I have God for my armor in coming against thee, who will destroy thee and all thy army by my hands for I will this day cut off thy head, and cast the other parts of thy body to the dogs, and all men shall learn that God is the protector of the Hebrews, and that our armor and our strength is in his providence; and that without God's assistance, all other warlike preparations and power are useless." So the Philistine being retarded by the weight of his armor, when he attempted to meet David in haste, came on but slowly, as despising him, and depending upon it that he should slay him, who was both unarmed and a child also, without any trouble at all.