1 Samuel 17:39-40

39And David girded his sword upon his dress, and endeavoured to go; for he had not yet tried [it]. And David said to Saul, I cannot go in these; for I have never tried [them]. And David put them off him.

40And he took his staff in his hand, and chose him five smooth stones out of the brook, and put them in the shepherd's bag that he had, into the pocket; and his sling was in his hand. And he drew near to the Philistine.