1 Samuel 17:38-41

(38) And Saul armed David with his armour, and he put an helmet of brass upon his head; also he armed him with a coat of mail. (39) And David girded his sword upon his armour, and he assayed to go; for he had not proved it. And David said unto Saul, I cannot go with these; for I have not proved them. And David put them off him. (40) В¶ And he took his staff in his hand, and chose him five smooth stones out of the brook, and put them in a shepherd's bag which he had, even in a scrip; and his sling was in his hand: and he drew near to the Philistine. (41) And the Philistine came on and drew near unto David; and the man that bare the shield went before him.

There is somewhat very interesting in this equipping David for the battle; in the putting on, and putting off the unsuited armour, and at length, choosing only a few stones from the brook. Surely without much enquiry, we may see the gracious lesson it teaches us, under this similitude. In going forth against the cursed enemy of our souls, no human armour, though burnished, and sharpened with the keenest edge, will answer our purpose. The enemy, as is said of the Leviathan, laugheth at the shaking of a spear. The sword of him that layeth at him cannot hold. Job 41:28. David went forth, as he saith himself in another place, in the strength of the Lord God: Psalms 71:16. He that prompted him to undertake the battle, armed him with strength suitable to it. The smooth stone of the brook, which was of God's own creating, and which no human heart had polished or worked upon, was a sweet type, that both the Lord's armour and the Lord's strength should nerve his arm to give it the full commission intended. And how didst thou come, blessed Jesus, and of what was thy armour composed, when, in thy victory for us, and for our deliverance, thou didst enter the lists alone, to vanquish Satan, and sin, and death, and hell, and the grave. Surely thine own arm brought salvation unto thee; and thy fury it upheld thee. Isaiah 63:5.