We are now coming near this famous combat, and have in these verses the preparations and remonstrances made on both sides.
I. The preparations made on both sides for the encounter. The Philistine was already fixed, as he had been daily for the last forty days. Well might he go with his armour, for he had sufficiently proved it. Only we are told (Sa1 17:41) that he came on and drew near, a signal, it is likely, being given that his challenge was accepted, and, as if he distrusted his helmet and coat of mail, a man went before him, carrying his shield, for his own hands were full with his sword and spear, Sa1 17:45. But what arms and ammunition is David furnished with? Truly none but what he brought with him as a shepherd; no breastplate, nor corselet, but his plain shepherd's coat; no spear, but his staff; no sword nor bow, but his sling; no quiver, but his scrip; nor any arrows, but, instead of them, five smooth stones picked up out of the brook, Sa1 17:40. By this it appeared that his confidence was purely in the power of God, and not in any sufficiency of his own, and that now at length he who put it into his heart to fight the Philistine put it into his head with what weapons to do it.
II. The conference which precedes the encounter, in which observe,
1. How very proud Goliath was, (1.) With what scorn he looked upon his adversary, Sa1 17:42. He looked about, expecting to meet some tall strong man, but, when he saw what a mean figure he made with whom he was to engage, he disdained him, thought it below him to enter the lists with him, fearing that the contemptibleness of the champion he contended with would lessen the glory of his victory. He took notice of his person, that he was but a youth, not come to his strength, ruddy and of a fair countenance, fitter to accompany the virgins of Israel in their dances (if mixed dancing was then in use) than to lead on the men of Israel in their battles. He took notice of his array with great indignation (Sa1 17:43): "Am I a dog, that thou comest to me with staves? Dost thou think to beat me as easily as thou dost thy shepherd's dog?" (2.) With what confidence he presumed upon his success. He cursed David by his gods, imprecating the impotent vengeance of his idols against him, thinking these fire-balls thrown about him would secure his success: and therefore, in confidence of that, he darts his grimaces, as if threatening words would kill (Sa1 17:44): "Come to me, and I will give thy flesh to the fowls of the air, it will be a tender and delicate feast for them." Thus the security and presumption of fools destroy them.
2. How very pious David was. His speech savours nothing of ostentation, but God is all in all in it, Sa1 17:45-47. (1.) He derives his authority from God: "I come to thee by warrant and commission from heaven, in the name of the Lord, who has called me to and anointed me for this undertaking, who, by his universal providence, is the Lord of hosts, of all hosts, and therefore has power to do what he pleases, and, by the special grace of his covenant, is the God of the armies of Israel, and therefore has engaged and will employ his power for their protection, and against thee who hast impiously defied them." The name of God David relied on, as Goliath did on his sword and spear. See Psa 20:7; Psa 118:10, Psa 118:11. (2.) He depends for success upon God, Sa1 17:46. David speaks with as much assurance as Goliath had done, but upon better ground; it is his faith that says, "This day will the Lord deliver thee into my hand, and not only thy carcase, but the carcases of the host of the Philistines, shall be given to the birds and beasts of prey." (3.) He devotes the praise and glory of all to God. He did not, like Goliath, seek his own honour, but the honour of God, not doubting but by the success of this action, [1.] All the world should be made to know that there is a God, and that the God of Israel is the one only living and true God, and all other pretended deities are vanity and a lie. [2.] All Israel (whom he calls not this army, but this assembly, or church, because they were now religiously attending the goings of their God and King, as they used to do in the sanctuary) shall know that the Lord saveth not with sword and spear (Sa1 17:47), but can, when he pleases, save without either and against both, Psa 46:9. David addresses himself to this combat rather as a priest that was going to offer a sacrifice to the justice of God than as a soldier that was going to engage an enemy of his country.

He disdained him - He held him in contempt; he saw that he was young, and from his ruddy complexion supposed him to be effeminate.

And when the Philistine looked about, and saw David, he disdained him,.... He looked about for his antagonist, to take a view of him, what sort of a man he was, expecting to see one much like himself; but observing a puny young man, he despised him in his heart, and perhaps looked upon it as an affront to him to send such a man to fight with him:

for he was but a youth; his age was one reason why he despised him, being, as before observed, about twenty years of age, and not come to his full strength, a stripling, as he is called, Sa1 17:56, another reason follows:

and ruddy, and of a fair countenance; looked effeminate, had not the appearance of a soldier, of a weather beaten veteran, exposed to heat and cold, and inured to hardships.

the Philistine said . . . said David to the Philistine--When the two champions met, they generally made each of them a speech, and sometimes recited some verses, filled with allusions and epithets of the most opprobrious kind, hurling contempt and defiance at one another. This kind of abusive dialogue is common among the Arab combatants still. David's speech, however, presents a striking contrast to the usual strain of these invectives. It was full of pious trust, and to God he ascribed all the glory of the triumph he anticipated.