| Clarke's Commentary on the Bible Saul armed David - He knew that although the battle was the Lord's, yet prudent means should be used to secure success.
Gill's Exposition of the Entire BibleAnd Saul armed David with his armour,.... Not with what he wore himself; for it cannot be thought he would strip himself of his armour in the field of battle, and when just going to it; and besides what suited the one would not be fit for the other, their bulk and stature being different i but this was some armour Saul had brought with him, besides what he himself wore, to furnish any with that might want it: and he put an helmet of brass upon his head; such an one, though not so large as Goliath had, these being usually made of brass; See Gill on 1 Samuel 17:5, also he armed him with a coat of mail; which probably was of brass also, and like that of Goliath's too, only lesser, 1 Samuel 17:5.
Geneva Study BibleAnd Saul armed David with his armor, and he put an helmet of brass upon his head; also he armed him with a coat of mail.
Wesley's Notes 17:38 Armour - With armour taken out of his armoury. He seems to speak of some military vestments which were then used in war, and were contrived for defence; such as buff - coats are now.
King James Translators' Notesarmed David...: Heb. clothed David with his clothes
Jamieson-Fausset-Brown Bible Commentary38, 39. Saul armed David with his armour-The ancient Hebrews were particularly attentive to the personal safety of their warriors, and hence Saul equipped the youthful champion with his own defensive accoutrements, which would be of the best style. It is probable that Saul's coat of mail, or corslet, was a loose shirt, otherwise it could not have fitted both a stripling and a man of the colossal stature of the king.
Matthew Henry's Concise Commentary17:31-39 A shepherd lad, come the same morning from keeping sheep, had more courage than all the mighty men of Israel. Thus God often sends good words to his Israel, and does great things for them, by the weak and foolish things of the world. As he had answered his brother's passion with meekness, so David answered Saul's fear with faith. When David kept sheep, he proved himself very careful and tender of his flock. This reminds us of Christ, the good Shepherd, who not only ventured, but laid down his life for the sheep. Our experience ought to encourage us to trust in God, and be bold in the way of duty. He that has delivered, does and will continue to do so. David gained leave to fight the Philistine. Not being used to such armour as Saul put upon him, he was not satisfied to go in that manner; this was from the Lord, that it might more plainly appear he fought and conquered in faith, and that the victory was from Him who works by the feeblest and most despised means and instruments. It is not to be inquired how excellent any thing is, but how proper. Let Saul's coat be ever so rich, and his armour ever so strong, what is David the better if they fit him not? But faith, prayer, truth, and righteousness; the whole armour of God, and the mind that was in Christ; are equally needful for all the servants of the Lord, whatever may be their work. | 
