31 And, hearing what David said, they gave Saul word of it: and he sent for him. 32 And David said to Saul, Let no man's heart become feeble because of him; I, your servant, will go out and have a fight with this Philistine. 33 And Saul said to David, You are not able to go out against this Philistine and have a fight with him: for you are only a boy, and he has been a man of war from his earliest days. 34 And David said to Saul, Your servant has been keeper of his father's sheep; and if a lion or a bear came and took a lamb from the flock, 35 I went out after him, and overcame him, and took it out of his mouth: and if, turning on me, he came at me, I took him by the hair and overcame him and put him to death. 36 Your servant has overcome lion and bear: and the fate of this Philistine, who is without circumcision, will be like theirs, seeing that he has put shame on the armies of the living God. 37 And David said, The Lord, who kept me safe from the grip of the lion and the bear, will be my saviour from the hands of this Philistine. And Saul said to David, Go! and may the Lord be with you. 38 Then Saul gave David his clothing of war, and put a head-dress of brass on his head and had him clothed with a coat of metal. 39 And David took Saul's sword and put the band round him over the metal coat, and was unable to go forward; for he was not used to them. Then David said to Saul, It is not possible for me to go out with these, for I am not used to them. So David took them off.
Matthew Henry's Commentary on 1 Samuel 17:31-39
Commentary on 1 Samuel 17:31-39
(Read 1 Samuel 17:31-39)
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.